 |
 |
||
 |
|
||
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
||||||||
 |
Planetary News: Cassini-Huygens (2006)Reports from the May 4-5, 2006 Meeting of the Outer Planets Assessment Group (OPAG)Special Coverage from The Planetary Society WeblogMay 4-5, 2006The Planetary Society Weblog is written by the Society's Science and Technology Coordinator, Emily Lakdawalla. She attended a two-day meeting in Pasadena in May 2006 of the Outer Planets Assessment Group, a body established by NASA to identify scientific priorities and pathways for exploration in the outer solar system. OPAG: A brief updateMay. 4, 2006 | 21:21 PDT | May. 5 04:21 UTC
It's already 9:00 and I've hardly begun assimilating my 16 pages of notes, so I am going to have to just post a short summary with some highlights from today's meeting of the Outer Planets Assessment Group, or OPAG. This group has the same basic charter as VEXAG, which I attended on Monday and Tuesday, but as you'll see the issues with outer planets exploration are substantially more complicated than they are with Venus exploration. Today's agenda included updates on the status of the Cassini and Juno missions; a couple of science talks; presentations on plans for Europa, including a mission study from JPL, and also one on a Titan balloon mission from JPL; presentations on the status of programs to build radioisotope power sources and on the Deep Space Network; and some other future tech stuff. The overarching message from today seems to be that outer planet exploration really requires a whole lot of things besides mission planning, and that without a coherent programmatic plan from NASA, the outer planets program is kind of in trouble. You can do inner planets missions on the cheap; and doing them relatively cheaply and frequently establishes a good skill and infrastructure base for continuing to do them frequently and cheaply, allowing you to have constant improvement in capability through incremental steps. But most outer planets missions, speaking realistically, cost a lot more, take a lot longer, happen more rarely, have longer gaps between them, and require a lot more investment in stuff back on Earth that is independent of the (often high) cost of the missions. In addition to missions, you need, first of all, communications. All deep space communications go through the Deep Space Network, and outer planets missions rely very heavily on the very largest telescopes in that network, the 70-meter dishes, which turned 40 years old this year. I'll cover my notes from this presentation in more detail later, but here's a couple of numbers to make you think: over the last 15 years, the number of spacecraft tracked by the DSN has grown 450%, while the number of antennas in the DSN has grown by 30%. Second of all, you need power. The Juno mission will manage at Jupiter on solar power, because it is avoiding the worst of Jupiter's radiation environment. But no mission to a Jovian moon, nor any mission to any target more distant than Jupiter, can get by with solar power; we need RTGs, radioisotope thermoelectric generators. Right now, the US has 15 kilos of plutonium-238 left for future RTGs, and 10 of those are earmarked for Mars Science Laboratory (MSL). We cannot do another outer planets mission without more plutonium. Even if we started this year, we couldn't start producing more until 2013 -- it would take that long to get our systems back online to turn our limited remaining supply of 300 kilos of neptunium-237 into plutonium-238 (at a production rate of only 2.5 kilos per year). But there are no funds in the budget to restart production this year, and in fact the program at NASA that develops more advanced technology -- including the new multi-mission RTG that MSL (and all future RTG-powered missions) will depend on -- had its budget cut by 30% this year because no future missions were being planned that needed the plutonium power supplies. It's a catch-22. Even if the funding were restored right now for starting a Europa mission, there's no guarantee that there would be plutonium available to power it when they need it. Third of all, you need scientists around who can analyze the data once you get it back. They haven't talked about this yet at OPAG, but they will first thing tomorrow: outer planets scientists more than any other planetary group depend upon funding from NASA in between missions to keep them alive professionally until the next mission comes along. Cassini is the only game in town right now; if you didn't get on Cassini, your only other source of funding is NASA's research and analysis funding. Which has been cut dramatically in the FY 2007 budget. The message has repeatedly been stated in the meeting room today that OPAG needs to come up with strong, clear, consensus messages to NASA about the need for investments in the DSN, investments in new power supplies, and, above all, plans for future missions. And I hope that OPAG produces all those things. In the end, though, it's not OPAG that leads NASA exploration of the outer solar system, it's NASA. And it looks as though we're beginning to see a program that is suffering from a failure by NASA to plan for the future. The present is extremely good, with Cassini in orbit and New Horizons on the way to Pluto. But there is only a single mission actually in the works for the future, and it's on the smaller side for outer planets: Juno. There has been a lot of talk over the years about going to Europa, going to Titan, and going to Neptune; there was even a presentation today about a Ganymede orbiter with a powerful enough camera to study Europa and Callisto too. But none of those things is actually being planned for future implementation by NASA, which means that nobody is planning for their power supplies or their data return capability or the scientists to support them. I'm afraid I'm going to have to leave you with that cheery message because I have to get some food and get some sleep. If you want to read more about what The Planetary Society -- and the public -- thinks about this situation, read our press release from today on our "Save Our Science" campaign. I hate ending on a negative note though, so please do check out my previous post with all the terrific new stuff that came out of Cassini-Huygens and Hubble today; and when I can I will post my notes from some of today's interesting presentations. OPAG: Looking backMay. 5, 2006 | 17:30 PDT | May. 6 00:30 UTC
The two-day meeting of the Outer Planets Assessment Group is over and I have 30-odd pages of notes to wrestle with. Just before I left the meeting today I had a five-minute conversation with the chair of OPAG, Fran Bagenal, and I have to say that before that conversation I was feeling quite a bit drearier about the whole thing than I do now. Being inexperienced with government or indeed anything that much involves people and their institutions (look at my college transcript and you'll see nary a sociology, law, political science, economics, or philosophy class), I'm not accustomed to the wrangling and the arguing and above all the way that individual people's personalities get involved in the whole process. It's all so messy. But somehow the process does produce space missions that themselves produce so many spectacular results that I don't have time to read about them all, and in the end this meeting involved that process actually working. Fran's attitude is basically that there is a crisis at NASA right now, but that things are getting better, that the voices of the community are being heard and actually listened to. We have to keep shouting, but we can shout knowing that it's making a difference. I hardly know where to begin, so I guess I will just go through in the order that the presentations were made at the meeting. Next up: the status of the next New Frontiers mission, the Juno mission to Jupiter. OPAG, Day 1: Cassini and Juno statusMay. 5, 2006 | 18:15 PDT | May. 6 01:15 UTC
The Outer Planets Assessment Group opened with the status of two of the three actual outer planets missions, Cassini and Juno. (There was no New Horizons status presentation for some reason.) Dennis Matson gave the Cassini update; most of what he presented was stuff I'd just seen at the Lunar and Planetary Science Conference in March. One new thing was a graph showing the data from a recent radio science Titan occultation, where they probed Titan's atmosphere by broadcasting radio signals at Earth as Cassini crossed behind Titan. "It turns out that the Ka-band gets absorbed at a higher altitude than these others," he said. (Ka-band has shorter wavelength/higher frequency than the X- and S-band radio signals that Cassini can also produce.) He didn't comment on what that actually meant, he just said the radio scientists were excited about the detail in the plots.
Next up was Scott Bolton, who reported on the status of Juno. Juno is currently in Phase B, which means they are working out the spacecraft and mission design but aren't building the spacecraft yet. Bolton spent the first half of his presentation explaining why their launch was recently delayed from 2009 to 2011. It doesn't have to do with any problem with the spacecraft design or mission plan. "We were originally proposing to a 2009 launch date; but upon selection, NASA informed us they didn't have the budget profile that was in the Announcement of Opportunity; they had a different one. Not only did they not have enough money, but it was kind of a flat profile. There was no bump. Typically a mission needs a big bump a couple of years before launch." That's when they need to establish contracts and start building the spacecraft and buy their launch vehicle and stuff. Bolton went on to say that NASA had told them strongly that they did not want the Juno project to "descope" or reduce their instruments or other capability in order to solve the budget problem. The best way to fix the budget problem was to take a delay to a later launch date. Launch dates in either 2010 or 2011 would have no negative impact on the science. In the end, he said, the budget profile in 2010 looked too risky, so they took the delay to August, 2011. (One thing that might have made the 2010 launch date possible was the cancellation of Dawn. However, Bolton was very careful to say, the budget overrun of Dawn is NOT what caused the delay to 2011. It was just an overall budget problem at NASA.) Of course, delaying a mission unavoidably increases the cost of the mission, Bolton said. "Unavoidable cost increases due to delay have to do with inflation; everything moved one year adds up to 4% of the total budget. Launch vehicle costs also went up by $36 million as soon as we were selected. Launch vehicle costs are going up across the board. All of the missions we have to launch are all going up in cost, just due to these increases in launch costs. Part of the reason is there aren't enough of them going." When there are fewer launches happening -- and it's not just NASA launches, it's the Air Force too -- then the fixed costs have to be spread over fewer missions, and everybody takes a hit. "What we have with that delay is a longer phase B. There are advantages to this; we'll retire more risk. The disadvantage is, every time you wait, you have inflation, you have the team dragged out, you have the potential for launch vehicles to go up again." Juno's status is currently "green" for all the things that NASA watches them for -- meeting their technical, schedule, and programmatic promises, which, Bolton said, is unusual. "By this point, many missions have realized they have to descope, or costs go up. We have yet to see any problems with our design. We are set up to work as a well-oiled machine." Clearly, the cost increases were weighing on Bolton's mind, perhaps because of the recent fracas over Dawn (though he did not say so). "All of the Announcements of Opportunity have the wrong numbers for the cost of the launch vehicle. Even if you don't ding the principal investigator for that, it all comes out of one pot. The general rule of thumb is that there are certain cost increases that projects may get because of something NASA imposes on them, such as a delay. NASA doesn't necessarily penalize you for that, but at some point they might say, we don't have the money, what are you going to do about it? We were directed not to take any descopes. Nevertheless it all comes out of all of our future. When Juno gets delayed, the Announcement of Opportunity for the next New Frontiers mission moves out, and everything gets smaller for our community." It's a problem, but nobody immediately had any solutions to suggest, and I guess there's really no solution; increasing costs are just a fact of life. So, so much for the budget situation. Bolton gave a quick overview of the plan for Juno. "We have a 5-year cruise, assuming an Earth gravity assist. The baseline mission is 32 orbits of Jupiter. The orbit is designed for a minimum of high radiation doses." They do this by having a highly elliptical, polar orbit that goes within 5,000 kilometers of the cloud tops at perijove and then swings up and out and around the worst of Jupiter's radiation belts. Over time, the orbit gets a little more dangerous. "Each orbit is about 11 days. The orbit evolves downward, so perijoves go northward; the trajectories go through redder zones of radiation belts at the end of the mission. We can accomplish almost all of our science objectives in the first half of the mission." Juno will be the first to be sent to Jupiter under solar power, with three huge solar arrays 11.5 meters long; and it's spin-stabilized. One thing I found interesting about the Juno instrument suite was that since it is designed primarily to study Jupiter's interior structure, composition, dynamics, and magnetosphere, a camera is really not a particularly important instrument. However, they will carry a camera, "which is mainly an education and public outreach tool," Bolton said. It would certainly be poor for public relations to go to such a pretty planet as Jupiter and not send back snapshots! The instruments that will actually be doing the heavy work include radio science, a magnetometer, a microwave radiometer, an energetic particle detector ("which has recently changed its name to JEDI," Bolton remarked), an auroral dust experiment, a radio and plasma wave science experiment, and an ultraviolet spectrometer. The coolest-looking instrument is the microwave radiometer, which by broadcasting radio signals into Jupiter at a broad range of wavelengths can detect its structure many kilometers down. This will help in part to answer a fundamental question about Jupiter: is it rotating as a solid body, or as concentric cylinders? "Grade school kids are amazed that we don't know the answer to this question," he commented. OPAG, Day 1: Getting to EuropaMay. 5, 2006 | 19:37 PDT | May. 6 02:37 UTC
Next up at the Outer Planets Assessment Group meeting was an overview of the plans for future Europa missions. All of this was being done in an environment where, three times, NASA has committed to at least studying a future Europa mission, and then reneged on that. It's not clear why getting a Europa mission started has been so hard. There has been consensus among scientists (well, with a few objectors, but they're scientists, there will always be objectors) since the end of Galileo's primary mission that Europa is the prime target for the next "flagship" mission that NASA should launch. There's clearly a lot of frustration in the outer planets community that the start has not happened, despite the fact that Congress explicitly directed NASA to start it. But there was a lot of constructive discussion over the two days of this meeting directed at what the outer planets community can do to get it started. First, Ron Greeley gave an overview of the Europa Focus Group, sponsored by the Astrobiology Institute, which holds workshops on all aspects of Europa. The most interesting thing from his presentation is that the astrobiology community has the same broad view of how Europa should be explored as the outer planets community does: send an orbiter first to do thorough reconnaissance, and follow that later with a lander with a specialized package that can study Europa's astrobiological potential (as well as other things). Bob Pappalardo gave a presentation on the refined science objectives for a future Europa mission. Whatever architecture or constraints are imposed on the mission to Europa, these are the community's agreed-upon list of the questions that should motivate the instrumentation and investigations performed by the mission; I already summarized them from the talk Bob gave to the outer planets community at LPSC in March. Here's the list:
You can read the full document discussing these objectives at the OPAG website (PDF format). After Bob presented these, Louise Prockter asked: "What do we do with this document now?" Greeley responded: "Once a document or words like this is crafted, it can be used in a lot of different places, like in any of these planning groups. But some of this, in relation to working on the Hill, may not be the kind of wording we want to use in working with a staffer. So we also want to take these and put them in terms that might be more appropriate for someone like the Planetary Society and [congressional] staffers." Next up was Karla Clark from JPL, presenting the results of the latest study performed by JPL of a possible Europa mission called Europa Explorer. Before she gave the presentation, there was a funny but awkward episode. Curt Niebur, who is the NASA HQ representative to (from?) OPAG, had to ask all foreign nationals without Green Cards to exit the room, because Clark's PowerPoint presentation had not been vetted by the office at JPL whose responsibility it is to make sure that none of the materials used in public presentations run afoul of ITAR, that International Trade in Arms Regulations law that has been so stifling to international cooperation. About a dozen people ruefully left the room including the two ESA representatives, Peter Falkner and Gerhard Schwehm, who were there seeking ESA-NASA cooperation on a future Europa mission! ITAR frequently has very silly and annoying implications for getting work done in space exploration. The silliest aspect of the whole thing was that just half an hour earlier I'd been asked by Curt to switch my badge for one that said "PRESS PRESS PRESS PRESS" on it in great big red capital letters on a yellow background -- it might equally have said "DANGER DANGER DANGER" -- yet it was okay for me to stay in the room! I feel sorry for the people who have to enforce these silly rules. I suppose that by reporting on Karla Clark's presentation I could run afoul of ITAR. But there didn't seem to be anything shocking in her presentation; and my experience from working with the rovers and ITAR issues leads me to believe that the pictures are generally the things that are considered more sensitive than the words, so hopefully I will not get into any trouble by summarizing Clark's talk. The JPL study was of a Europa orbiter, specifically a Europa Geophysical Explorer. "The study said: what if we used only existing technology?" Clark began. Existing technology removes roadblocks to a launch soon. Clark said there were two caveats: they planned to have a new radioisotope power supply that is being developed for Mars Science Lab, and they allotted mass for a lander but did not study what that lander would look like, how it would land, or how it would be instrumented. The mission outline would go like this: "It has 1.5 years of Jupiter system science because we would spend a lot of time getting our velocity down to where we can get into orbit around Europa. This is followed by a 90-day prime mission around Europa." However, if they can build a spacecraft that performs as well as Galileo did beyond its design lifetime, "we're talking upwards of a year in orbit around Europa," Clark said. "For science instruments, we're looking at 180 kilograms, 10 instruments, including a high-res imager and a sounding radar. And we had 340 kilograms of unallocated mass, which could be used for system robustness, additional radiation shielding for a longer lifetime, or a lander." Someone asked: "Is that enough of a mass margin to go to a smaller launch vehicle?" Clark: "No." The proposed mission would launch on a Delta IV Heavy, using a Venus-Earth gravity assist trajectory. Clark explained that they had looked at using a smaller launch vehicle -- an Atlas V -- but that it was just cutting the mass margin too close. "We took this mission and tried to put it on an Atlas and it did not work. You might be able to do a different mission on an Atlas, but not this mission." "One of the issues we dealt with is getting data back from Europa. Radiation-hard memories are difficult. We came up with a system that returns gigabits per day, 250 times as much as Galileo." Someone asked whether that was all through the Deep Space Network, and she said yes, and that they were assuming 24-hour-a-day access to DSN resources during the 90-day nominal mission. Clark explained that previous Europa mission studies had been hampered by the requirement of a direct-to-Jupiter trajectory (no gravity assist, hence more restricted mass) and a lack of understanding of the exact difficulties imposed by the radiation environment at Jupiter. "With a direct trajectory you come up with a 1-ton spacecraft; with an Earth gravity assist -- 2 tons; with VEGA [Venus-Earth gravity assist] you get about a 3-ton spacecraft. The cost of increased mass is increased flight time. Direct is about 3 years; EGA is about 5; VEGA is between 6 and 8 years. "We've spent several years taking Galileo data and incorporating that into a model of Jupiter's radiation environment, so we have a big advancement in the radiation-hard components and subsystems. There have been developments in radioisotope power systems (RPS) and what we've come up with is an orbiting mission that is feasible with current technology." Clark showed a graph comparing the proposed Europa Explorer to the proposed Europa Orbiter mission that was cancelled in 2001. I suspect that this comparison had a little bit of salesmanship in it, with some likely optimistic numbers, but one of the contrasts really stuck out. For the Europa Orbiter, the mission had a nominal length of 30 days and it could not be extended for planetary protection reasons. Clark explained why. "All orbits around Europa are unstable" because of the influence of Jupiter and the lack of understanding of Europa's gravity field. "This is something we didn't really understand in the original Europa Orbiter. The eccentricity grows very rapidly, and uncontrolled orbits impact Europa on the order of one month. That is dependent on which orbit you're in. There are some orbits that take longer to impact, but it's very, very dependent on what gravity field is and we don't know what that is. We can find them once we are there." With the new proposal they would go into orbit, figure out the "J3 values" (a parameter describing the difference in the shape between Europa's northern and southern hemispheres), and then make adjustments. "Once you know what the J3 values are, you know what orbital eccentricity gives you an orbit that is 'frozen,' then you would have to move the orbit." The fact that they can keep their orbit stable means two things: their nominal mission can be longer -- minimum 90 days -- and they can extend the mission as long as they can be sure that they can control the spacecraft. Another big challenge has been Jupiter's radiation environment. Radiation is bad all around for a spacecraft but one of its worst effects is on memory -- that is, on the data that the mission will be returning. The JPL proposal solves this problem by keeping data in memory for as brief a time as possible. "We assumed that for a short period of time, we could get continuous coverage by the Deep Space Network. This has been done before; we felt 90 days was pushing it. We'd have 300 Megabits of storage on board for science data; we ended up with 21 Gigabits per day. It's a realtime mission -- you use onboard memory as a buffer, and you send the data down." Someone asked whether that required continuous coverage by the largest, 70-meter dishes; Clark said yes. Talking about the possibility of using the 340-kilogram margin for a lander, Clark showed a few concepts that other working groups had developed, and where they weighed in. An impactor required around 100 kilograms; airbag landers ("Europa Pathfinder") came in at a bit over 200; soft landers came in between 300 and 400, with one outlier at 800. So, she argued, a soft lander is probably not possible, but an airbag assisted lander could be. However, there was a bunch of muttering among the people sitting around me to the effect that a lot of the 340 kilograms would probably be eaten up in the 20% mass margin imposed as a risk-mitigation strategy, and there were questions about whether it could be better used for other things -- like, for instance, a scan platform for the optical remote sensing instruments. However, Clark pointed out that their proposed design included a gimbaled main antenna in order to keep up that continuous data transmission to Earth; that would make a scan platform much less necessary. (Cassini lacks either a scan platform or a gimbaled antenna, so it can either take pictures or communicate but not both, something that has made planning Cassini's mission very complicated.) Someone asked if this study included a cost analysis. Clark said it did not, and that there were a lot of factors that made cost hard to pin down; she finally said "I like to say it's 2 plus or minus 1 billion. It depends upon a lot of things that are outside of our control: launch vehicle, instrument cost, whether or not there is a lander, and whether the new radioisotope power supply is available." It seemed that this presentation was regarded as interesting and a good start -- but not official enough; it lacks the detail to really determine whether it is feasible. Still, Bill McKinnon remarked, "Overall, I think this is much more comprehensive and realistic than the previous studies." With Clark's presentation over, the foreign nationals were allowed to return to the room, which was good because Gerhard Schwehm was next on the agenda, talking about ESA's plans for a Europa mission. He explained that while ESA wants to go to Europa, the mandate of the mission had to be much broader than that. "The three themes: characterize Europa as a planetary object and a potential habitat; study the origin, formation, and evolution of Jovian satellite system; and Jupiter system science: atmophsere, magnetosphere, and nebula. This group is not only focused on Europa but on Jupiter system science. In Europe you have to have much broader focus in order to get the support of the scientific community. If we get one mission to Europa it will be many decades before the next one." He said that the appeal would be broader because of the presence of Juno. "This is complementary to Juno, because Juno focuses on Jupiter; this mission would focus on satellites. The two address Jupiter's magnetosphere and atmosphere in an ideally complementary way." The architecture that ESA is looking at is very interesting. "The themes can be addressed by the combination of a Europa orbiter and a Jupiter orbiter relay satellite. A lander element was considered but is not currently foreseen as feasible within the budgetary envelope. We would like to have a lander, but in the group we are realistic that we stay within a budget limit." The mission can be proposed to ESA in a process beginning in the middle of this month, Schwehm said. "Responses will be due mid-October, and we would like to complete down-selection by early next year. Out of the ESA-NASA Europa working group, we hope we can have a team that proposes a mission to Europa and the Jovian system and we hope that the participants in the ESA-NASA Europa orking group will participate in the preparation of mission proposals. We hope that if we pass the first round -- that is, if the Europa mission proposal is selected for assessment study -- that NASA will be able to commit to a joint ESA-NASA study team. We have to see how under present ITAR regulations we can work. We have demonstrated in the past we can work. If we do not do that, the next 10-15 years will be a problem. The community at ESA believes that Juno and the newly proposed ESA-led Europa mission will form two ideally complementary components of an international Jupiter System Exploration Program; close communication between the two mission teams will maximize synergies and science return. I think that with the budget situation on both sides of the Atlantic, we have to do our best to get the most science out of our decreasing budgets." Schwehm handed over the floor to Peter Falkner, who talked more specifics about the proposed ESA mission design. "The configuration is one Europa Orbiter and one Jovian relay spacecraft. We know from the radiation environment around Europa that orbiter lifetime is very limited. We came to the conclusion it was better to have an orbiter to relay data more slowly to Earth, even after the Europa orbiter is already dead. We don't bring to Europa what we don't need there. And with additional relay satellite it is easier to address other Jovian system science topics." The mission architecture would be about a 1-ton spacecraft, launched on a Soyuz-Fregat into a Venus-Earth-Earth gravity assist trajectory, taking 6 years to reach Jupiter if launched in 2017 or 2023. ESA is considering either chemical thrusters or solar electric propulsion. The relatively small mass, split between two spacecraft, gives a very small payload of 34 kilograms on the Europa orbiter and 16 on the relay satellite. "Because of the mass challenge, we are looking into a highly integrated payload suite. We marry all instruments together as much as possible, reduce harness, and reduce multiplication of subsystems." This proposed mission sounds pretty cool but it will be competing against many other proposals; and unlike NASA, ESA doesn't have all these different divisions between the Mars, outer planets, astronomy, and heliophysics groups; all of these branches compete together. So it's unclear what the chances are that a Europa mission can make it through this process at ESA; but it's clear that ESA thinks Europa exploration is a priority, and they want to work together with NASA on it. I hope NASA can make things work better with regards to all that ITAR stuff to allow this cooperation to happen. My eyes are crossing so that's going to be it for today. I've gotten through about half my notes from yesterday; a day and a half worth of notes remain, and I'm off to join my colleagues at the International Space Development Conference tomorrow! OPAG, Day 1: Hot-air ballooning on TitanMay. 6, 2006 | 10:46 PDT | 17:46 UTC
The next presentation at OPAG was given by Ralph Lorenz and Tom Spilker on a Titan Montgolfiere Mission Study. What's a Montgolfiere, you ask? Maybe you know but I didn't know that it's a hot-air balloon -- hot-air, that is, as opposed to lighter-than-air. In other words, they were describing a possible future mission to Titan in which you would inject a probe that would inflate a balloon with Titan's own atmosphere and then just heat it in order to establish neutral buoyancy. It's an intriguing combination of 21st-century space flight with century-old technology.
Ralph opened the presentation by showing a cute picture that Jonathan Lunine had put together, where he framed one of the side-looking Huygens descent panoramas inside an airplane window. "The airplane window view is what this is really all about," Ralph said. "With Huygens, we essentially had a 3-hour cross-country flight that was cloudy for most of it." A Titan Montgolfiere would give you the airplane window view of Titan for weeks, even months or longer. "Titan is a very diverse world," Ralph said, "so we don't want to send either a lander or a rover." He showed several of the examples of interesting terrain visible from Cassini RADAR images, and pointed out that most topography on Titan is apparently slight, under a kilometer or so. "If you float a balloon at 2 or 3 kilometers, you're likely to be safely above everything." Furthermore, unlike a lighter-than-air balloon, which must vent limited gas to land and then drop limited ballast to rise, a hot-air balloon can drop simply by not continuing to heat its envelope, then rise by heating it again. Of course you need a heat source, which typically requires the burning of a limited supply of fuel, but the Titan Montgolfiere would use a radioisotope heat source and thus wold be able to go up and down, even sampling the surface for in situ studies. Ralph outlined a possible intrument package for the Montgolfiere's gondola (how quaint!): a subsurface sounder; a near-infrared spectrometer; a tunable laser spectrometer; a sonic anemometer; imaging cameras; a pressure/temperature sensor; a gas chromatograph mass spectrometer; and a surface sample analysis package. That package could include a sample acquisition mechanism; another gas chromatograph mass spectrometer; an age dating package; a surface hardness instrument; a sample context imager; a sample microscope imager; and an elemental analysis package. "Age dating," Ralph said, "is a throwaway remark. In Titan's atmosphere, you would produce radioactive carbon as you do on Earth, so we may be able to identify how fresh the aerosol deposits are." The whole thing would be topped with a steerable high-gain antenna that would be capable both of direct-to-Earth communication and, more importantly, relay to a small orbiter. The relay orbiter could also carry a radar imager/altimeter; a near-infrared imaging spectrometer; and radio science. Ralph gave the floor to Tom Spilker to talk more about the nitty gritty details of how a Montgolfiere mission would work. "For a first mission going to the detailed study of Titan, the Montgolfiere is the optimal way of handling that mission. Titan is ideally suited for an aerial vehicle. Titan has a large scale height," -- scale height is a term that atmospheric scientists use to describe how rapidly the density of an atmosphere goes down with increasing altitude, and Titan has the largest scale height of any planetary atmosphere -- "and because of that you can get a soft entry into the atmosphere. It's the easiest place in the solar system for aerocapture." Aerocapture is kind of like daredevil aerobraking. Instead of aerobraking -- which Mars orbiters have used (and are using) to brake slowly into Mars orbit by gently dipping into the topmost part of the atmosphere, aerocapture involves a single dive into a much denser part of the atmosphere. It's never been used in an actual mission, but other presenters at this meeting said that the theory was ready and was just waiting for a technological demonstration. Tom continued: "Titan has high-density, high-molecular-weight, low-temperature air. Below 10 and 20 kilometers, the winds are low-speed and prograde." That is, the global wind patterns generally follow the direction of Titan's rotation. "Below 10 kilometers, winds are retrograde at times. This allows you the flexibility of drifting in one direction for a while," eastward, or prograde, "going down and drifting back toward an interesting target" to sample it. "The most promising implementation is a hot-air balloon, which rides the wind at about 10 kilometers, jetliner altitudes, where the winds move slowly enough that you can make decisions to, if something really looks interesting, make a decision to go down and look at things. So far, with the RADAR, wherever we've looked, we find multiple interesting things in there. We think it will not be a problem to find interesting things to look at. We're looking at imaging at 1-meter resolution" from that 10-kilometer altitude. So how are they going to get a balloon deployed on Titan? "We've verified that with reasonable entry devices, we can put out the device necessary to deploy a balloon. There is enough time and enough energy to inflate and stabilize a balloon at a decent altitude and go on an exploration program that includes landings. We are not breaking new ground with deploying balloon from parachute; it has been done on Earth. "The first thing we do is establish the direct-to-Earth link, look around, and establish our bearings. We do that by beginning imaging, and do image-based navigation. The first landing site is a contingency sample. You want to make sure that the first data that you get back is interesting, so you want to bias the entry point to one of these interesting spots. (Ganesa, Xanadu, or Huygens site, for example)." When could we go? "Using chemical rockets, about 3 years of every Jupiter synodic period (which is about 14 years) gives you a gravity assist window. Solar electric propulsion widens that a bit. The aerobot would have direct entry; because of the large scale height you can go almost straight down, which gives you a lot of targeting flexibility. The orbiter requires aerocapture. Aerocapture hasn't been demonstrated yet; we're waiting for an opportunity, it's on the threshold, waiting for deomonstration." Tom went through a few simulations that showed how the balloon might drift across Titan during its mission. It turns out that the wind models for Titan agree with each other in the higher-up parts of the atmosphere, and they agree with the Huygens descent up to a point, but at the lower reaches of the atmosphere where the balloon would reside, they actually diverge quite a lot; one model has the winds going prograde pretty much all the time, the other has them switching to retrograde once each Titan day because of tidal effects. Both would see the balloon drift northward and southward a little bit with each Titan day, ending up covering I guess about 15 or 20 degrees of latitude and all 360 degrees of longitude. One of the biggest challenges to this mission would be relaying the data to Earth. The balloon "would have direct-to-Earth capability, but the time-averaged data rate would be only 1 to 2 percent of the total data volume." The rest would be returned by the orbiting relay satellite. "With a 180-day aerobot mission, you would get about a Terabit back, about 5,000 times Huygens, similar to Mars Global Surveyor and Odyssey. You could have a 5-year orbiter mission -- that should last quite a bit longer than the aerobot. Depending on the orientation of the orbit, data latency can be considerable." Data latency means how long it would take from the time that the aerobot captured the data to when it was able to be returned to Earth. "It can be many hours to a week. Contact times would be 50 minutes maximum, brief pulses of very high data rate. In fact, the science data acquisition capability far exceeds the downlink capacity, so autonomy is going to be important. You prioritize reduced data for downlinking. You do classification and compression and manage storage for downlink schedule. You produce higher-level products onboard. You also use autonomy to drive a landing." Tom explained that a "landing" would not actually involve touching the whole gondola to the surface. "'Landing' means winching down a payload from a gondola, 50 to 100 meters below the gondola. We've flown these at Earth before." There were many questions from the audience. One asked how much power would be needed to heat the balloon. "We need 2,000 Watts to fly a vehicle like we describe here," Tom replied -- an answer that got a low whistle from the audience. But, he clarified, "This is not electrical output, it's heat output. You'd only need a single MMRTG." Radioisotope thermal generators generate electricity for a spacecraft from the heat created from the radioactive decay of plutonium. Current RTGs are actually not very good at turning the generated heat into electricity; they only have a few percent efficiency, and only produce tens of Watts in electrical output. But the balloon wouldn't need the heat converted into electricity -- it can use all the power present in the raw heat output, so 2,000 Watts is not a crazy number. Another question had to do with the readiness of the technology. Tom answered, "the mission concept is achievable with further maturation of current technologies. Some are currently in process -- for example, the MMRTG on the balloon. That needs to be taken fully to completion. This is feasible; the next step is significant pre-phase A studies." Kevin Baines asked whether there is really time to deploy, inflate, and heat a balloon during a ballistic entry into Titan's atmosphere. Tom: "Yes. It turns out it's easily doable. You don't deploy and heat in 15 seconds; it takes 2 or 3 hours. It takes minutes to deploy, but several hours to heat; you descend 30 kilometers while you're heating." Recall that it took roughly two hours for Huygens to descend to the surface under a parachute. Another person asked whether precipitation is an issue, and to this question, Tom and Ralph had to say yes. "Precipitation" of course means rain, or worse, snow, methane rain or snow. Ralph said, "During certain seasons, there are certain latitudes we will want to avoid. Raining on a Montgolfiere is not a good idea. Another thing that is not a good idea is icing. If you get up above 17 kilometers you run into problems with icing. We haven't solved problem of rain, but there are tacks you can take that show promise." This proposed mission is still somewhat in the "pie-in-the-sky" stages, but it sounds ready for more detailed study. Balloons have been suggested for exploring lots of places in the solar system, and the Russians used them with success on Venus. I'd love to see a balloon mission to Titan happen. One final note about this presentation -- throughout the rest of the meeting, it seemed that people who didn't want to call it the "Titan Montgolfiere" took to calling it "Ralph's balloon" instead, and finally, yesterday, Ralph had to interject "It's not my balloon!" OPAG, Day 1: Uranus equinox is coming upMay. 6, 2006 | 11:05 PDT | 18:05 UTC
Heidi Hammel gave a brief but spirited presentation designed to wake up the audience to the fact that Uranus is fast approaching its equinox, an event that will happen on December 7, 2007. The approaching springtime for the northern hemisphere has already produced dramatic changes in Uranus' cloud features. (See "No Longer Boring: 'Fireworks' and Other Surprises at Uranus Spotted Through Adaptive Optics.") Heidi pointed out that Uranian equinoxes are quite rare; the last one was in 1965, and the next one will not be until 2049. (Curt Niebur joked that "with that lead time I can get it in the NASA budget.") There was a workshop for two days in the middle of this week of an international group of planetary astronomers talking about what the Uranus equinox observing campaign should be: science objectives, measurement objectives, which telescopes to request time on for what sorts of observations, that sorts of thing. One of the most interesting observational events, which I hadn't thought about before, is that when Earth crosses Uranus' ring plane (which it will do twice in 2007 and once in 2008, because Earth's orbit is slightly tilted with respect to Uranus' orbit -- ring plane crossings do generally happen three times for every giant planet equinox), we will get to observe "mutual events" of Uranus' satellites. Now, I've written a lot about the nifty mutual event movies that Cassini has made by watching one Saturnian moon passes in front of another. The movies that ground-based telescopes will make of the much more distant Uranian system will not be visually spectacular in that way; they'll just be points of light. However, by watching how one satellite dims the light of another, and then spending a ridiculous amount of computer time crunching that light curve into a computer model, they can figure out the large-scale patterns of brightness and darkness on the surfaces of these bodies. This is exactly how scientists have produced "maps" of Pluto and Charon, by observing the light curves from their mutual events. And remember that because Voyager passed by Uranus when it was near its southern summer solstice, half of the entire globes of all of Uranus' satellites were in winter darkness, their surfaces nearly invisible to Voyager's cameras. Our maps of these worlds have virtually no detail in their northern hemispheres. Observations of these mutual events will let scientists make the first maps of the northern hemispheres of Miranda, Ariel, Umbriel, Titania, and Oberon. And without any plans for a return to Uranus over the next fifty years or more, these observations are as good as it's going to get in the professional lifetimes of all active planetary scientists. The punch line of Heidi's presentation was to formally request OPAG to draft a letter to NASA expressing support for the next two years of ground-based Uranus observation surrounding this equinox event; such a letter will help the planetary astronomy community win telescope time and grant funding to put out an extra effort to observe Uranus during this unique period. Nobody in the room had any objection; it's going to be a really cool few years for Uranus science.
OPAG, Day 1: Status of radioisotope power and communications support for future missionsMay. 6, 2006 | 15:08 PDT | 22:08 UTC
Following the mission- and science-focused presentations of the morning, there came two rather alarming presentations: one on the status of the "RPS Program" (RPS stands for Radioisotope Power Supply) and one on the status of the Deep Space Network. Both of these programs are run by NASA independently of the funding of any particular mission, although of course both respond to the demands of present and future missions -- everything is linked. The presenter was Ajay Misra, from NASA Headquarters. "The GPHS RTG used on Cassini is no longer in production." That stands for General Purpose Heat Source Radioisotope Thermoelectric Generator. "But we have a lot of spare parts, so we can maybe produce two more of these units; if we are lucky we can get three. So we decided a few months back we would invest some money. Two or three could be available for flight 2012 and beyond." The limiting ingredient in the production line apparently is a thermocouple that is no longer in production, and whose production would be difficult and expensive to restart: "It would be 40 to 50 million dollars to restart the line, and there is no other customer but NASA. But we can do better than this. "You heard this morning about future uses for the Multi-Mission Thermoelectric Generator (MMRTG) Development. It is designed for use on Mars and subsequent RPS-powered missions. The product is to be available in 2009 for Mars Science Laboratory." The basic specs: nominal power: 125 Watts at beginning of mission; 100 Watts after 14 years. Misra showed a slide listing the numbers of radioisotope power supplies needed for the missions that the science community (if not NASA) has been discussing doing over the next couple of decades; the list was far too long for me to write it all down. Misra summed it up as "Lots. We need a lot of these things. But there is nothing in the budget for RPS for any of these missions. Delay and uncertainty of future science missions have resulted in a significant reduction of the RPS budget. 'You don't have anything in the future, so you don't need the money.' So they cut us by about 30 percent." His presentation moved on to some explanations of the kinds of RPS that will follow after the MMRTG has been developed, including one with a Stirling design. The MMRTG will not achieve significant increases in efficiency over the current RTG design; the Stirling will enable them to get more power out of each kilo of plutonium. And that, as it turns out, is a goal we need to be aiming at, for reasons Misra explained next. (I have to say I also found this presentation interesting for its open discussion of plutonium supply; as a kid of the Cold War, it seems strange for us to be chasing Europeans out of the room one moment and talking openly about our plutonium supply the next. There were no ITAR restrictions on Misra's talk!) There is a paucity of plutonium-238. "5 kilograms has been delivered from Russia; 5 kilograms more is on order." These orders are to supply the plutonium necessary for the Mars Science Laboratory mission. Each future MMRTG, which will produce roughly 100 Watts of power apiece, requires I think 2.9 kilograms. "Russia has only 15 kilograms of inventory beyond MSL. The Department of Energy can buy 5 kilograms more under its current contract. There is an option in the contract for it to be extended to purchase the remaining 10 kilograms. "The DOE is proposing to produce plutonium-238 at Idaho National Laboratory. The US has 300 kilograms of neptunium 237, the feed material for producing plutonium 238. Production is proposed to start in 2013. There would be 5 kg/year of production, of which 2.5 kg/year for NASA use. But there is no budget yet for starting production at INL -- it has always been proposed as over the guideline, and request has been stopped at OMB." They could not show actual missions that need to use this material, so the OMB has balked at paying to start the production. "So right now nobody has put the money to the Department of Energy to start producing." Someone in the audience asked whether Russia is capable of producing more. Misra: "Russia can produce more if they are paid to. Their production is shut down right now but they can start it pretty easy; easier than us." Someone asked Misra how much neptunium-237 the Russians have, and he didn't know; that particular question, again, tickled my Cold War sensibilities; how preposterous it would have been to ask that question 20 years ago! Curt Niebur commented, "Russia has also realized last year that NASA really wants plutonium. Prices have gone up from $2.4 million to $2.7; they will probably go up above $3 million per kilogram." Just one more thing to raise the cost of missions. Misra finished with a request that OPAG support a more robust investment by NASA in the development of future radioisotope power supplies and the plutonium-238 necessary to power them. I have to comment that I'm not unsympathetic with the OMB not funding plutonium production when there aren't missions that need it being planned. That is what needs to be fixed -- NASA has got to say that they do plan future missions. Then there will be no reason not to fund plutonium production. The technology investment is another matter; and that's a theme that was also raised by VEXAG on Monday and Tuesday. NASA has more to do than plan missions; it's also got to investigate in new technology developments to enable those missions. Which brings me to the next talk, which was given by Bob Preston, on the status of the Deep Space Network, which is called the DSN by pretty much everybody in the space business. Preston came out swinging. "Over the next 30 years, deep space communications will have to accommodate orders of magnitude increases in data transmitted to and from spacecraft, and at least a doubling of the number of supported spacecraft. The present architecture is not extensible. So NASA must develop a new strategy so that the DSN is no longer a restriction on mission capability, but instead an enabler." First, Preston explained the current situation with the DSN, and why it's not "extensible." "The DSN has three major sites around the globe, with 16 large antennas. It currently services about 35 spacecraft for both NASA and foreign partners. A large number are planetary, but a significant number are heliophysics, astrophysics, and technology demonstration missions. DSN is of course the spigot for all of science data and is part of all radio science experiments. At a cost of $2 billion, it is a good deal. But many of the current DSN assets are obsolete or well beyond the end of their design lifetimes. For example, we have just celebrated the 40th anniversary of the 70-meter antennas." And the 70-meter antennas, he said, cannot be upgraded to support the higher-data-rate Ka-band transmissions that are being deployed with newer spacecraft. This aging infrastructure is being asked to support a vastly expanding fleet of spacecraft. "Future US missions will require a factor of 10 more bits returned per decade, and a factor of 10 more bits sent per decade. Spacecraft will require more precision navigation for entry, descent, and landing, as well as outer planet encounters. And improvements are also needed to support human missions. "NASA has neglected investment in the DSN over the decades. Compared to 15 years ago, the number of DSN tracked spacecraft has grown 450%, but the number of antennas has grown by only 30%. Drivers on demands on the DSN are increased complexity and performance of missions. We've gone from brief flybys to detailed orbital remote sensing. Three orbiters at Mars are constricted largely by communication time." In other words, we are not getting back all the data that we could from our spacecraft at Mars, because the DSN is a bottleneck. "We're going from short-lived missions to long-lived missions." Also, the demands are increasing from non-planetary missions, because they are orbiting father and farther from Earth. "We're going from low-Earth-orbit missions to much more distant orbits; Spitzer, which trails Earth in its orbit, now needs the 70-meter dishes. And we're going from single spacecraft to arrays." The latter point hasn't happened yet; but there are missions on the drawing board that include whole clusters of satellites being launched as part of a single mission. "Where we'd like to be in terms of data rate is around 5 Megabits per second; but Cassini, for example, is only capable of just shy of 80 kilobits per second." At this point Preston was interrupted with the question: "Can the needs of human exploration be leveraged to improve the DSN assets?" Preston's reply: "Human exploration is interested in Ka-band communications. However, at the Moon, you don't need big antennas. You do need high-data-rate systems, so there is a possibility of leveraging there. "By 2030, we need a thousand times the downlink performance increase, and there'll be two times the number of spacecraft. What process is NASA using to plan for the future of the DSN? NASA and JPL have developed a DSN roadmap. This is being integrated into an agency-wide program plan by the Space Communications Architecture Working Group, or SCAWG," which Preston pronounced "scay-wig." "Mike Griffin has declared that NASA has neglected the DSN and communications infrastructure, and requested a plan to deliver to Congress by 2007." The new and improved DSN will not look the same as the old DSN with its 35- and 70-meter dishes. "Radio communication with large arrays of small antennas will be the backbone. This would serve all missions -- large, small, new, old. Costs will be recovered over time through much lower operation and maintenance costs. Now we have antennas from 26 to 70 meters. For the arrays we are talking about antennas ranging from 6 to 18 meters, hundreds at each site, to meet our requirements. This isn't ridiculous because radio astronomers already do it." Someone in the audience asked how the DSN will save money by increasing the number of antennas, replacing single antennas with arrays. He answered, "Right now, every antenna is different. We want to go to a system where the antennas are nearly identical, where some fraction will always be down for regularly scheduled maintenance, with a centralized, automated maintenance strategy. Right now there's a lot of manual work, with an operator at each antenna. Large radio telescope arrays have a single operator, who often does maintenance as well." Preston went on. "In addition to the ground-based assets, we know that for assets like probes, landers, and rovers, that it's much more efficient to get data back not direct to Earth but to go up to an orbiter around that body and then come back to Earth. Almost all data from the Mars Exploration Rover mission is coming back that way. So orbital data relays at Moon and Mars are in the plan. Eventually, optical communication would be brought in, with trunklines from Mars to the Moon." In other words, spacecraft may always carry radio antennas; but one orbiting telecom satellite at Mars could receive the communications from all Mars orbiters and landers and relay it via a much higher-data-rate optical transmitter to Earth or the Moon. "Small antenna arrays have more resiliency and redundancy, more graceful degradation of performance in case of antenna or receiver failures, and they are easily scaleable when growth is required -- build it in parts, build it as you need it. You can track many spacecraft at once instead of having one big antenna on one spacecraft. We would just pile up the right number of antennas instead of wasting surplus aperture from one large antenna." The DSN has experience with this kind of arrayed communications already, Preston said; it was used by Voyager for its operations at Uranus and Neptune; by Galileo; and even Cassini uses arrayed 34-meter antennas. Finally, Preston explained the DSN's plan for increasing data rates the factor of 1,000 that is needed for the future. The new antennas give you a factor of 10 increase. Switching over to higher-frequency Ka-band communications from the current X-band gives another factor of 4. Another factor of 5 are will come out of advanced coding and compression of the data itself. And another factor of 10 will be achieved with higher-power spacecraft transmitters. That's it for the first day of the meeting (phew!). Now on to the second day. OPAG, Day 2: Update from the NASA Advisory Committee meetings this weekMay. 7, 2006 | 20:09 PDT | May. 8 03:09 UTC
During the first day of OPAG, the chair of the group, Fran Bagenal, was not present because she was participating in some rather important discussions taking place in Maryland. She came in on Friday morning to give a lengthy update. Her update contained a rather more thorough explanation of the structure of all of these committees and subcommittees than I'd heard at VEXAG, so things are making slightly more sense to me now -- but it's still all kind of a blur to me what goes on in Washington, with all the groups and advisory bodies and their overlapping responsibilities and individual agenda. Fran began: "As you know, the Solar System Exploration subcommittee which used to exist as an advisory body to NASA HQ was disbanded some time ago. It's been replaced. There is now a new thing called -- as it's always been called -- the NAC [NASA Advisory Committee]. This one is chaired by Jack Schmitt, who is a lunar geologist and astronaut, the first scientist-astronaut. His agenda is to go back to the Moon -- you know that's why he's been put there, to go back to the Moon. "There's a subcommittee, for science, chaired by Charles Kennel. Also there are Wes Huntress, dear friend of the planetary science community; Mark Robinson; Neil Tyson --" here she made a disgusted looking face, someone asked her why, and she said "he was the dastardly person who said Pluto wasn't a planet! -- and there's Eugene Levy…so actually we have a good group for planetary science, pretty heavy in science. That is the science subcommittee of the NAC. Then there are 5 subcommittees that map directly on the subdivisions of NASA -- astrophysics, heliophysics, Earth sciences, and planetary sciences, and a fifth one called the planetary protection subcommittee." The Planetary Science Subcommittee is headed by Sean Solomon. "We -- the four science subdivisions -- met together and in separate groups and talked with the people from NASA HQ and discussed various things. Sean Solomon appointed me as his vice chair, because he felt it was important that the outer planets community was represented. "We started off with Harrison Schmitt, who's 'return to the Moon, return to the Moon.'" While Fran, as an outer planet scientist (and in agreement with pretty much everyone at OPAG as well as VEXAG), would like to see less of a focus on the Moon, Fran had to admit that "I got him to sign my copy of his book. "We [the Planetary Science subcommittee] are going to write a letter in the next three days, which we will then send to the science subcommittee of the NAC, who then meet next week or the week after. We can't say, 'don't go back to the Moon,' obviously. But we can say, if you have any spare money, this is where we'd like you to put it. If you have to take some money away, don't take it from here. So we can give some advice, and it is heeded. Sean Solomon had been instructed to form working groups from the different disciplines. He said we already had working groups, those are the 'AGs.'" (e.g. OPAG, VEXAG, MEPAG.) "More than any other division, we've got our act together here in the solar system. So we should proceed knowing we have some influence, we're listened to, and we're not wasting our time. "So these committees are all under the Federal Advisory Committee Act or FACA. This means all meetings have to be open, have public record and so forth, all members have to be vetted." (She described the comical situation of trying to explain her retirement investments to the lawyer responsible for this vetting process: "I'm like, 'I don't know, it goes into a hole and comes out eventually.') "The advantage of FACA is if we give advice to NASA through this structure, NASA has to respond. There is always a point where there has to be a response, for the public record. So that's where the power is. If there's any sticks it's there." At this point I wrote in my notes, "My brain hurts." To summarize how I think this all works: NASA Administrator Mike Griffin wants input from the science community to come through the body called the NASA Advisory Council, which is headed by Apollo astronaut Harrison Schmitt. Sitting directly on the NAC are five people who represent the "Science Subcommittee" of the NAC, chaired by Charlie Kennel. (Other, parallel subcommittees represent aeronautics, finance, human exploration, and human capital.) Then there are five science advisory bodies that can feed input to the Science Subcommittee; the one we are concerned about is the Planetary Science Subcommittee (is it actually a "sub-subcommittee?"), which is chaired by Sean Solomon and vice-chaired by Fran Bagenal. (Other, parallel entities represent heliophysics, astrophysics, Earth sciences, and planetary protection.) All of these committees exist under the FACA framework, so all of their meetings and interactions must be part of the public record. I think. Fran continued, "Mike Griffin recognized he made a mistake in dismantling the advisory structure before he put the new one in place; with no way to receive advice, mistakes were made. He said [the cuts to] R&A was his mistake. He emphatically said, 'We are going to the Moon.' He's been told we're going back to the Moon. He was appointed because he wants to go to the Moon. That isn't going to change. Secondly, it's clear he wanted to get rid of the ISS [International Space Station] and shuttle as soon as possible, but he can't, because of international agreements. We have to deal with return to flight, 16 plus 1 shuttle flights are on the manifest, and ISS has to be paid for. This is the big problem. He wants to get CEV going, and he's got these costs associated with shuttle and ISS. And he's found ways, he says, in the case of planetary science: if the argument is first to go to the Moon, then to go to Mars, then Mars missions down the road were premature in that we're not going to Mars yet, we're going to the Moon. So that's where most of the planetary science money was removed. Of the 2.9 billion that came out of science, 2.7 came out of Mars missions. That does not mean the cuts to R&A and astrobiology were not serious. But that's where most of the money from SMD [the Science Mission Directorate within NASA] was removed. "Next we had Mary Cleave, who gave her standard pitch on the NASA budget. She says that the NASA budget has been growing, SMD has been growing, it's not going to be as fast as it was originally planned to grow." This is indeed the same pitch she gave at that awful Lunar and Planetary Science Conference 'NASA night.' "We all know that the budget growth is actually associated with things like full-cost accounting, increased cost of launches, and mission delays causing cost increases due to inflation and other things. But there were also additional missions going in there. The argument is we, SMD, should curb our appetite, and it comes down to less than inflation growth, in real dollars it's a decline. And so the biggest hits were to solar system, mostly out of the Mars line. "So then we broke off and went into the groups. And we had a meeting with Andy Dantzler, and several of you sat through these meetings. We looked at the budget, and Andy took various approaches to looking at ways in which we could restore R&A. We were looking at 5 years, 2007 through 2011. There's a question about whether the 2006 operating plan could be changed. The 2006 operating plan was passed to Congress, who then some people on the [Congressional] science committee responded with, 'you took more money out of Mars, you took more out of astrobiology, and you haven't started with the Europa mission like we directed you.'" Jeff Moore interrupted to ask: "How responsive does NASA have to be to that?" Mark Sykes responded: "If NASA were to ignore that, they're not authorized to spend more than 80% of their budget until Congress approves their operating plan, so they would get a 20% hit across the board. Basically the letter was telling them that 'we have report language, we told you to do things, you didn't do it, come back to us with an operating plan that conforms, and then we'll let you go forward.'" Fran Bagenal returned to her summary. "So what we were presented by Andy was an argument. We could leave things the way they are, or we could do various things. For instance, we could restore R&A by cutting the 2011 Scout opportunity, by cutting the Discovery mission that was the AO [Announcement of Opportunity] just completed, or we could add a flagship and cut both. So he went through various drastic scenarios. So we had lots of debates about this budget that he presented -- we asked him, 'What's this here? What's that there?' He fairly explained a number of them, but the problem was, he presented pie charts that took the whole five years; it was very coarse in terms of scale. We were arguing to him that the fix we need to do is probably at a higher resolution than they were presenting. It's true it's not easy to solve this, there's not a big slice of fat you can just cut off. "There is some reality that if you take a mission and delay it, you don't just move that fixed amount of money out, you incur some fixed costs. This is not an easy problem to solve. At some point, you end up just delaying the problem. He kept on talking about bow waves, delaying the problem." Mark Sykes: "That's why it's best to talk about delaying something that hasn't started yet." Fran Bagenal: "There's an advantage in cutting something before the money stream starts going. So that's why things like the 2011 Scout and current Discovery AO were targets. "Now this is where things got a little messy. A lot of people in the room were involved in those particular events," Discovery and Scout. "So there was a big issue about conflict of interest. I may actually have my name on a Scout, I'm not sure, so I had to go out of the room along with a lot of other people. It turns out that all the other divisions had the same problem. So when we reported back at the end of the day we couldn't come to a conclusion because none of us had been in the room; we were stymied by the lawyers. So the way we resolved this in the end is: we could talk in generalities or euphemisms. So if you wanted to talk about restoring Scout, you could talk about restoring 'this kind of thing.'" There was a lot of head-shaking in the audience. "The bottom line is, we did strongly support restoring R&A. I spoke up saying that I thought a 50% cut to astrobiology was extremely damaging. People who know me know I don't like astrobiology, but a 50% cut is devastating. A 30% cut, in a humane way, you don't need to renege on current commitments -- you miss a year. But if you cut 50% you have to renege." Someone pointed out that indeed, most R&A grants run three years; a 30% cut means you have to skip a year but you don't take any already-awarded money away. Curt Niebur: "But I should point out that with astrobiology it gets a lot more complex because in addition to the grants, you have the astrobiology institutes," long-term entities that are independent of the 3-year grant programs. Jeff Moore: "What's the cost to cut just new people in astrobiology?" Curt Niebur: "I don't know." Amy Simon Miller: "In all this discussion, who trumps who? Congress said, 'you shouldn't cut 30 million from aeronautics,' they say nothing about R&A. Clearly there isn't enough money to do all of these things." Fran Bagenal: "What we were talking about with Andy Dantzler was priorities within the budget. So things like aeronautics are a separate issue. Even Mars is a separate line. So the message we gave was the Planetary Science subcommittee, representing the solar system exploration community, feels that R&A is important and should be restored. "So we then had a bit of a reprieve; Thursday morning we had half an hour of statements from the community. Some people were supporting specific missions, but many people spoke in favor of R&A. It was half an hour of impassioned speeches. I heard a lot of people say afterward that it was a really good session. That it didn't come across as hysterical; it was rational argument as to why we needed to support R&A and small missions. "We then went back to Andy Dantzler and talked about the budget and the plan. There's a Congressionally mandated plan that NASA has to come up with, a strategic plan for science. And we all think, 'yet another plan. But Headquarters, in fact Andy Dantzler, has to come up with a plan for planetary science, and they're trying to, in a hurry and we're talking months, write a planning document. So obviously they're taking the material that's there, the roadmap, the decadal survey, and we're like, 'who's writing this?' And it's HQ staff. And we're like, 'wait a minute, can we help you?' So the next step is this document, which I wrote this on the plane last night. We have to get this in, because if we don't they will write 'Mars' instead of 'giant planet.' I'm exaggerating, but the Mars guys are really slick; we, the outer planets community, have got to get our act together." Curt Niebur: "This science plan needs to be done in the next few months because Congress wants it this fall, but NASA wants the 'AGs' to look at it, the National Research Council to look at it, and they all need time for input." Fran Bagenal: "So what we looked at was, the four mission statements were almost word for word the same as in the Roadmap document. In that document you have five mission objectives, and they've been merged to four. I think they're fine. Then there's four mission destinations, and this is what we have some discussions about. Inner solar system, which includes the Moon, Outer solar system, which is us, Mars, and primitive bodies, which is also us. We're going through a phase of our science where we're debating what's a primitive body and what's not, but it's basically a way to talk about smaller bodies in the solar system effectively. "So we then had a presentation by Melissa McGrath of the Strategic Roadmap. At lunchtime we had a presentation from Len Fisk to the whole SMD community; Griffin was there too. Fisk is chair of the Space Studies Board that advises NASA on what to do. So it has been mandated that the Space Studies Board will review the 2007 budget. They've done a review of the 2007 budget and got it out in 6 weeks, which is incredible. Griffin came to hear what he had to say. And what they said was, you won't find screeching that says 'you must do this,' what you will see is some bland words, but underneath that the message is quite strongly that R&A and small missions are very important. That the amount of money that has been removed from R&A, microgravity and life sciences, they said those should be restored, pointed out these are only 1% of the NASA budget. They said to Congress, give NASA 1% more to fix R&A. There's no obligation from Congress to do this, but Congress asked for their advice, and they got it. "It's clear that Griffin and Cleave didn't realize they were opening up this hornet's nest. They didn't realize this would let loose a national furor. They got the message. I'm fairly confident that the R&A funds, not necessarily all of them, there will be some restoration. How much will go into the 2006 operating plan I don't know. There was a lot of damage done in what was going on in 2004, 2005, and 2006 budgets, associated with the fact that the advisory structure was disbanded. Now it's understood that we're watching very, very carefully." Sushil Atreya: "Is Andy Dantzler going to come back to you?" Fran Bagenal: "Yes, the Planetary Science subcommittee is meeting again in July. We will discuss the budget more. There's going to be a big lunar science conference in October discussing lunar science that should be done for science's sake, and lunar science that is enabled by human exploration of the moon, so we have to address that. It is organized by NAC -- it's Schmitt's conference. Sean Solomon also identified technology as being key to what we need to talk about, particularly the outer solar system. "I then talked with Andy Dantzler about, he asked me, should he write a letter for OPAG, and I said no, don't write a letter, he and I sat down and we went through various items. I said let's go over the letter that we wrote to him and go over these issues. "Andy Dantzler claimed that he really tried to have the [Europa] flagship study happen, but he was told that since there was no money in the out years to start the mission, there was no point in having a phase A study. I argued, there is a point in having a phase A, because the big issue that we have is: does a Europa mission fit within a flagship box? You then have to describe what the flagship box would be. Completion within 15 years -- achieving a mission within a budget of, say, 2.8 billion, for scale. Describe a box and have a decent study that requires substantial funding and time to figure out whether it fits in that box. We have to be able to say 'yes' or 'no.' If we have, unfortunately, to say no, we have to put it aside and go on to something else. We've done lots of Europa studies, but none of them has been done with sufficient fidelity to figure out once and for all whether we can do it or not. My feeling is we need to write a letter that goes to Andy Danztler. He argues he would like to have such a study happen, but he's basically been directed not to do that, and I talked to Mary Cleave, and she basically wants to put it off. I think we have to be persistent with this." If what she's saying isn't clear here, it's this: No one knows how much the Europa mission will actually cost. We can't figure that number out until something like a "phase A" study of the mission is performed. Fran is arguing that NASA must spend the necessary money -- whatever that is, likely a number in the high single digit or low double digit of millions -- to do a thorough enough preliminary study to figure out what it will take. And the outer planets community needs to be prepared to accept the conclusion of that study; if it winds up with a mission costing around 2 or 2.5 billion dollars, they should press for NASA to do it. If it would cost more than 3 billion or more, the outer planets community must be prepared to drop it in favor of something else more feasible. Gregg Vane: "Just a few weeks ago, both Ed Weiler and Charles Elachi met with Mary Cleave, and compared and contrasted science return from flagship versus Discovery missions. They made a very strong point that we have to have flagships. Mary Cleave made no reference to that this week." Heidi Hammel: "I think they were discussing Cassini, Voyager, and Hubble -- those were the examples they were using." Fran Bagenal: "How do we get flagship missions started is a crux issue. All the divisions are facing this, but it's absolutely critical for OPAG." Someone asked: "How much to do a study?" Fran Bagenal: "The rule of thumb is, through the end of phase B, you need to spend 10 percent of the mission. So if it's a $2.5 billion mission, that's $250 million. So the question I asked Gregg last night is, what do you need to do a pre-phase A? What do you need to spend to know, given a certain cost sizing, time frame, and availability of technology, what can you do, or does it achieve the goals we have laid out in that box? the answer is probably on the order of 5 to 10 million." Vane agreed. Another question: "What was spent on yesterday's JPL presentation" of their proposed Europa Explorer? Jim Cutts answered: About $600,000. Gregg Vane: "How much do you have to spend to be confident? Over the years at JPL, to get to the point where you can come within at least 30% or better of the final cost you have to spend about 10%." Fran Bagenal: "The point is, we should put in our letter, very strongly state, describe what it is we need to have studied, describe what the plan is." Someone said: "I don't think the money issue per se is the problem, it's the philosophy." They were referring to a reluctance on the part of NASA to fund any part of a Europa mission -- or a flagship mission. Following this was a presentation by Jim Cutts on the "Roadmap" document, but this was not a lot different from the one he'd given to VEXAG. There was some discussion at the end about the over-optimism of the roadmap, which defines the rate at which missions should happen in the future: 7 Discovery missions per decade, 4 New Frontiers missions per decade, and 1 to 2 flagship missions per decade, depending upon their size. However, most people agreed that that proportion was the correct one. Still, it was also clear that the outer planets group in particular absolutely requires missions on the more expensive end of the scale -- New Frontiers at a minimum, flagship level for the most part. I think that most of the people in the room recognized that this is a bad year, and that they're all going to have to accept some losses this year. But they were also all hoping -- because they absolutely have to keep this hope -- that NASA is going to want to do flagship missions to the outer planets again. Which context makes it kind of interesting that the next couple of presentations were on the kinds of outer solar system studies that do not require flagship missions (yet): Mike A'hearn talked about Deep Impact, and Mike Brown talked about Earth based studies of small bodies in the solar system. OPAG, Day 2: Ground-based study of the small bodies in the outer solar systemMay. 7, 2006 | 20:10 PDT | May. 8 03:10 UTC
After the political discussions of the morning, Mike Brown stood up to give the "highly subjective view of one ground-based astronomer," he said. "Mostly I call them 'small bodies' rather than 'primitive bodies' because I see them as test particles of the planet formation process. The analogy that I like to use I got out of some EOS publication, where there was a freighter going across the northern Pacific and all these float toys fell off the freighter. These things float around and land in different places, and oceanographers used where they landed to figure out the currents and the winds. The Kuiper belt objects are kind of like that. "To do this, you need to know where these are. The big second-generation surveys are DES (NOAO), CHFT, and Palomar. The key result from the surveys is this plot." He showed a graph of all known objects, plotted by their semimajor axis versus their eccentricity, and talked about how it could be divided into many distinct populations. "13 years ago, before any of these objects had been found, I don't think anybody really believed that Neptune had migrated. So we've slowly been figuring out these populations. "The major things that are still unknown: inside the classical Kuiper belt, there are two entirely distinct populations. One is a low-inclination population, and one is a more extended-inclination population. These are in exactly the same place in space. It's very difficult to do that mechanically; it's like trying to heat up only half of a cup of coffee. The other big one is the radial distribution in the Kuiper belt. You get a big peak right around 43 AU, then there is a big dropoff right around 50 AU. "What you'd like to be able to do is take one of these plots like from Hal Levison, let it evolve over time, and you eventually plow outward through the Kuiper Belt, and finally Neptune migrates out and depending on the exact choice of the initial conditions you end up with a distribution of Kuiper belt objects and compare them to the real one. But you can't. The reason you can't is because of the biases in the surveys. The initial surveys were focused on finding objects. Even the second-generation surveys were focused on finding objects, not on recovering them. The best one is CFHT. They realized that recovering objects takes 3, 4, even 5 times as much time as finding them in the first place. This is a problem that has yet to be solved. We really know that the Kuiper belt doesn't extend out from 50 to 80 AU. But you can't see anything out beyond 100, because most surveys don't look for anything moving that slowly. "One other population that I like to talk about, are objects that are really out beyond the Kuiper belt. Sedna -- when we first found it we thought it would be circular or scattered. We were really hoping it would be circular. We were shocked when we figured out what it was, and it's THAT." His initial graph was a plot of the current locations of objects in the Kuiper belt, projected on the plane of the solar system; Sedna sat just beyond the belt, but not far from it. Then he dropped in Sedna's orbit. The Kuiper belt shrank to cover less than a tenth of the slide, and the orbit of Sedna swept way out in a gigantic ellipse that always remained far outside the Kuiper belt, as far or farther than its current position beyond the Kuiper belt. "It never comes close to an outer planet; there has to be something out there beyond the Kuiper belt. This thing is probably ½ or ¾ the size of Pluto. If you have the same size distribution of objects out there as you have in the Kuiper belt, then you have a substantially larger population." There was some quibbling about this; it's kind of poor practice to create statitstical arguments from very small numbers. "There have been now a dozen proposed models for how Sedna got there. Planet X; a single rogue star; or you form the Sun inside a dense cluster and what you're seeing is the Oort cloud that was formed at the outer part of the solar system. It's pretty easy to figure out which is happening once you find other bodies. "Nothing that we can see from Earth is remotely primitive. Most of the objects that are big enough to study have had processing; even if they aren't, their outer bits have been processed. For a long time, spectroscopy has been a serious disappointment. Very few objects show spectra that look very interesting. In the past couple of years, larger objects have been found that help in two ways. They're brighter, so you can get more signal, and they have more interesting surfaces. "For a long time Pluto remained unique; it was quite exciting to finally find something that was spectroscopically similar, 2003 UB313. The major difference is that UB313 is not red in the visible. It looks like UB313 is like Pluto but it doesn't have the dark spots. We don't see any photometric variation with rotation -- we don't know what the rotation is because we don't see any variation. It could be pole on, it could be not rotating, or it could be homogeneous. It does appear to be really high albedo, 85% albedo. It's a very bright icy surface. "FY9 has incredibly saturated methane lines. The way to get saturated lines is to have the path length through the ice be very long. You have 1-centimeter grains of methane ice on this, which is absolutely crazy. The model requires some ethane, much smaller grains, in tiny dark patches. None of these stories make sense when you compare to Pluto and UB313. We have a nice class of objects to study. "Something like 10% of these objects have largish satellites. But of the four largest objects, there are six satellites. If you look at the formation models for Kuiper belt satellites -- Robin Canup essentially predicted outer, small, icy satellites, because when they form from an impact the outer satellites are made of the icy mantle. EL61's satellite is a big block of ice. There is no Kuiper belt object that looks like these satellites of the largest Kuiper belt objects. "Outstanding future questions: the most important question for studies of the outer Kuiper belt are the birth of the sun, and the evolution of the solar system. For large objects, all the same questions you can ask about Pluto. For all the other objects, it's figuring out what we're looking at. One of my biggest disappointments is Spitzer and its poor performance at 70 microns. The 70-micron channel is just not that good. "There is no NASA program for this whatsoever. There are no thoughts about programs, telescopes, whatever. But that's OK, because we're doing fine. "New survey capabilities: Pan-STARRS: 2007+. These claims of dates are never exactly right. If done correctly, you could actually do the Kuiper belt job right. Discovery Channel Telescope in 2009. LSST in 2012. These are the things that can do the most important work out there. All seem to be going strong. "New followup capabilities: laser guide star adaptive optics at Keck; Gemini and VLT adaptive optics are coming online. CARMA, ALMA, EVLT, JWST, and TMT (thirty meter telescopes). It's an odd conclusion: NASA really hasn't done much, but that's OK. What can NASA do? Invest a comparatively tiny amount in R&A. Otherwise, we can get a free ride on the backs of the astrophysics community. If you cut off the R&A, all of this just stops. Actually it doesn't stop because the VLT has really taken over the Kuiper belt work. Having 4 telescopes and a kajillion instruments and a thousand people, they've taken over the field of physical characterization. [I wrote in my notes here: it's nice to hear someone not complaining.] "All these new surveys, very few people involved with them have much experience with the realities of ground-based surveys and the horrible consequences of weather. I am skeptical about how well these things are going to work. If you really want to do it right, you put a 2-meter telescope in space with a 1-degree field of view, which could cover 180 degrees per day to 25th magnitude. 3 years gives you all objects in the outer solar system to 25th magnitude. That's my pipe dream; sign me up for that." |
||||||||
 |
 |
||||||||
[ what is this? ]