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Headshot of Emily Lakdawalla

Deep Impact live blog

Posted by Emily Lakdawalla

04-07-2005 1:45 CDT

Topics: mission status, explaining technology, comets, comet Tempel 1, Deep Impact

So I'm back at JPL now, ready for a long night. It is a bit of a zoo here in the media room. There are a lot of people with laptops and headphones, clearly attempting to focus as they write, some of them talking to themselves. There are people trying to figure out what's going on. There are people speaking authoritatively about what's going on. There is a British TV crew wandering around, repeatedly attempting to film what is clearly the opening segment to a special on Deep Impact.

Several television monitors in here are displaying NASA TV. This much I could see on my couch in my living room, and probably with a lot less distraction. But there's an energy here at JPL, even if it's only among the people who are gathered to report on the mission. It's very different from the energy among the science team, I am sure. The science team is probably poring over the new pictures coming down from the spacecraft, cracking nervous jokes, and laughing too loud about them. The reporters are focusing intensely, trying to figure out when and where to capture the best information about the mission, trying to ignore the chaos, hoping that whatever happens tonight, they'll get to witness it.

Ay ay ay. Someone is filming me. Why are they filming me? Must not have been able to get into the science area or mission control, so all they can do is film the reporters.

Anyway, not much is happening in mission control right now. Clearly the spacecraft is still working fine, because pictures are still coming down.

Jul 3, 2005 | 21:11 PDT | Jul 4 04:11 UTC: Commentary on the imaging

The engineering teams that are busily monitoring the AutoNav imaging for flyby and impactor just made some comments about the targeting of the two imagers. I'm trying to follow along with the spacecraft imaging on the Deep Impact website, but I have to admit I'm having a hard time understanding what the images are showing. My understanding is that the Impact Targeting sensor was supposed to capture a pair of images -- one exposed for the comet's coma, one for the nucleus, at the following times (relative to the encounter time):

  • -22 hours
  • -20h
  • -18h
  • -16h
  • -14h
  • -12h
  • -10h
  • -8h
  • -7h
  • -6h
  • -5h
  • -4h
  • -3h
  • -2.5h
  • -2h
  • -1.5h
  • -1h
  • And then "more and more rapidly until it is acquiring images every 0.7 seconds."

So up to this moment -- just under 2 hours prior to impact -- there should have been about 15 pairs of ITS images. But I find 117. Some of them are really small -- are they thumbnails? I'm not sure what they are supposed show.

There was just a flutter of activity around the monitors. It sounded like they were talking about new "OD" information -- that means "orbit determination." What's going on is that they don't actually know the comet's orbit well enough to have targeted it beforehand; they have to determine the orbit based upon the observations that the impactor and flyby craft are making right now. This is not how navigators like to fly a spacecraft.

Stay tuned...

They've got the volume in here turned up now, so we can hear what's going on in mission control. There is some stuff like orbit determinations about 5 kilometers off what was expected, which is pretty good targeting. But then there's hairier-sounding stuff, like "we have a rejected command from the impactor." And, later, "this is not an expected rejection."

We just heard an interesting detail about mission control. Apparently, the people monitoring the flyby craft are wearng blue; the people monitoring the impactor are wearing red. Convenient.

The first ITM is coming up in only 5 minutes.

They've computed the change in velocity (delta V) they'll need, and the spacecraft has turned in order to point its thrusters in the right direction...

I don't understand all of what's being talked about in the MSA but there is a lot of activity going on. I'll try to take down some of the comments...

"We have a channel in red alarm, this is expected."

"Can you report on the flyby S-band receiver during ITM?"

"We are continuing to hold S-band lock."

"All impactor stations, you can expect a 4-5 minute telemetry delay at this time due to file management." (That has to do with the fact that the flyby craft is madly relaying information from the impactor, and falls a little behind during the ITMs.)

"We are currently receiving an image and there are 75 telemetry files in the downlink queue."

"We are back on target ID2." A fist in the air, must have been good news.

"Everything looks good."

It appears that the first burn was nominal! So far so good...

According to the impactor accelerometer, error on the thruster firing was only 0.35%, which is pretty darned good!

The reporter from Aviation Week just confirmed that his understanding of all of the conversation that just took place was that only a minor course correction was needed -- changes in targeting of only about 5 kilometers -- and that the course correction was performed nominally.

Jul 3, 2005 | 22:06 PDT | Jul 4 05:06 UTC: OD

Now most of the chatter is the various controllers figuring out exactly what happened in the trajectory correction maneuver, and then they need to figure out their orbit determination again, and then report what the AutoNav thinks it needs to do for the next maneuver.

"Another update on our OD status, we seem to have converged to B-plane coordinates 2.0 and 2.3." Based on chatter I heard earlier, I think that means they need to adjust their targeting by 2.0 kilometers in one coordinate and 2.3 in the orthogonal one in the next maneuver. But I could certainly be wrong about that. Those numbers are smaller than the first maneuver, which was 5 km in each direction, which is what you would expect.

I'm trying to pull pictures off the website, but it's clearly buckling under the strain of traffic.

11 minutes until the next maneuver...

The second of three trajectory correction maneuvers for the impactor is now underway!

The chatter is involving lots of numbers, but they are very hard to hear over the audio feed we are getting. Some numbers are describing course corrections in kilometers; others angular motion, measured in microradians. It's pretty hard to understand what's going on from here. Even the Aviation Week reporter -- who seems to be the one the other reporters are looking to for more technical understanding of what's going on -- is having a hard time getting it all.

We just saw a grainy shot of the images that are being returned from the High Resolution Imager on the Flyby craft, which are NOT being streamed out onto the web. They are resolving the nucelus beautifully. It's shaped sort of like a pear or avocado, but seems to have a big hole in one side!

But there is a nice flat spot on the "bulb" of the pear -- I think they have a good, sunny, flat spot for the impactor to aim for...

"...so a big hooray for the ground nav team," the mission controller just said. To translate: the ground navigational team has predicted the location of Tempel 1 to within one kilometer of its actual location. That's pretty good.

11 more minutes until the next, and final, trajectory correction maneuver.

Here's a quick and dirty sketch of what I saw on the monitor when they were showing those high resolution images of the comet nucleus.

Deep Impact sketch 1

They are still talking about AutoNav images, and apparently the mission controllers like what they see. Unfortunately the website that is feeding the impactor targeting sensor and medium resolution images out to the public seems to have broken down, at least from where I'm trying to access it. I hope I get to see more of those high resolution images soon. I'd like to improve on my sketch!

Just saw it! Here's my next sketch:

Deep Impact sketch 2

There really does seem to be a big hole in one side of this comet; some of the darkest pixels on the comet are in the shadowed wall of that hole (at least that's how I interpret the picture). Around the hole are also some darkish regions. I am not sure whether those are dark because of geometry (topography) or because of some color on the surface of the comet.

The final burn looks like it'll be similar in size to the previous ones. They're going to change the speed by about 2.3 meters per second, shifting the target by 1 or 2 kilometers.

"We are just completing turn to ITM-3..." (They seem to switch between saying "TCM" and "ITM," or "Trajectory Correction Maneuver" and "Impactor Targeting Maneuver."

I am now hearing that they are indeed targeting for that brightest area at the bottom of the bulb of the pear. It turns out to be quite a good geometry for impact, because the spacecraft will be flying underneath the comet as seen from this point of view. Everything is looking really good.

Except my view of the TV set! Now all the reporters are crowding around, all trying to get a good view...

Just minutes away!

The final imapctor targeting maneuver was "right on." All fault protection has been turned off for the impactor -- "you're on your own," the fault protection team said. The impactor is about to meet Tempel 1...

Five minutes away...

it is very very quiet in here now...

20 seconds to imaging sequences on flyby that will capture impact...

20 SECONDS TO IMPACT!!!

"Flight, this is telecom, we have lost the lock"

I just saw more images, "X marks the spot," there is a spot in between two circular dark rings on the bottom of the comet -- where the impactor is aimed --

The pictures are getting fuzzier, images are being degraded because of dust hits?

We've been looking at the same picture for a little while now...two very clear circular features, just above the "X" marking the aim point of the impactor...

"We still don't have confirmation of the impact, that will come a little bit later..."

CELEBRATION!

"Put that on the screen!" They are applauding, but what are they seeing?

It's a huge spray! They did it!!!!!!!!!

There is absolutely no question -- you can see a continuous cone of ejecta from the bottom of the comet in the high resolution images, coming out at a pretty shallow angle!

Here's my sketch:

Deep Impact sketch 3

"We have an image 3.7 seconds before impact."

The images of the impact are tremendous. I can't imagine what my old teacher Pete Schultz is doing right now -- he must be bouncing all over the science area. That blast of ejecta looks just like one of his experiment. This must be the culmination of his career.

So images are still coming back, but the spacecraft is just about to where it needs to turn into shield mode to protect itself from the worst of the comet dust surrounding the nucleus.

A reader just sent me this screencap:

Deep Impact post-impact (raw screencap)

We're now looking at pre-impact images taken by the impactor. There is so much detail. It looks to me like a surface that has been eaten away -- which may be sort of what happens as stuff sublimes off the comet and into space. There are two large obvious circular features, which my brain interprets as craters, but they could also have an endogenous origin, that is to say that they could have formed from some internal comet-jetting process.

But my eye keeps returning to that blast image. That comet is 15 kilomters long, and the object that hit it was the size of a washing machine, and that blast is absolutely huge. All the stuff that we can see in that cloud is fresh comet stuff -- stuff that may not have seen the light of day for more than 4 billion years. Leftover solar system ingredients that have been in the freezer all that time. It's just amazing.

The commentator is saying that the impact is bigger than he expected. But I'm going to reserve judgment on that until I hear Pete Schultz talk about it. Though, knowing Pete, I am wondering if he is going to be able to get a coherent sentence out of his mouth at the press conference. He is pretty incoherent normally. Now, he'll probably be utterly incomprehensible. But I'm sure his excitement will be communicated quite clearly...

The website is teasing me...I can see thumbnails of cool images, but can't download the full ones! Here's a tantalizing thumbnail...

Deep Impact thumbnail

A laugh from the reporters just now. Various Congresspeople have just shown up in mission control. The joke is that they never appear until a mission is successful, then they suddenly come out of the woodwork...

I've just heard from my coworker Jennifer Vaughn, who's at the Comet Bash that the Society is hosting for the public to view what's going on with Deep Impact. she said: "What a night! The event has been great. We have about 800 people here, the speakers have been great, and, of course, the mission rocks!"

We just saw a tremendous Medium Resolution Image of the moment of impact -- there is a huge flash off the bottom of the comet, just as Pete predicted.

I'm also beginning to hear from readers, which is great. I've been supplied with this image, the one I've been talking about from the Impactor Targeting Sensor, just prior to impact:

Nearly the last moment before Deep Impact's Impact (raw screencap)

The impact happened somewhere along that horizontal line between the two circular features. Look at that detail! Now of course the comet looks very bright against the blackness of space but that's not because the comet is icy. In fact most comets are very very dark, darker than asphalt, because the icy stuff has vaporized from the surface, leaving behind tarry gunk that's very dark. This picture looks bright only because the camera is sensitive, and the image was exposed long enough to make the dark comet look very bright.

The NASA TV commentator just said that the mission controllers have just been told they need to stop celebrating and get back to monitoring their mission -- the flyby craft is still going! The funniest thing about that comment is that she is currently interviewing Charles Elachi, the director of JPL, i.e. the boss of all those guys. He doesn't seem too concerned.

We are coming up on the moment of lookback.

This time, I think it was just applause for the team. All the guys in red shirts in mission control -- the erstwhile monitors of the impactor -- are done. Their spacecraft is dead. But, unusually for space missions, that was intended, and they can celebrate the dramatic death of their craft.

The images that they are showing are fabulous. Here's another screen cap from that reader (THANK YOU!)

Tempel 1 at the moment of impact (raw screencap)

This one was taken by the medium resolution imager and shows the impact flash, right on the bottom of the pear, below that hole. Just where they were aiming. The color commentator they had on the NASA TV coverage kept saying he was amazed at how large the flash was. For me, I'm not sure if I'm amazed at the size of the flash, but it seems to be so broad, at such a wide angle. I'll have to ask about that if they don't talk about it at the press conference.

They've stopped the NASA TV coverage. The press briefing will be in an hour. The other reporters in the room are settiing down to work. I feel like there's probably not a lot more I can do until I see the processed images that I hope they will release at the press conference.

I just overheard an interesting comment from one of the newspaper reporters. He said that if the mission had not produced these dramatically flashy images, they wouldn't be front page news tomorrow. Because of that flash, though, they will be. Isn't that something? Regardless of the existence of the flash or not, the fact that they managed to hit a comet with half a spacecraft, and watch it from another, would be an astounding breakthrough. But it's the flash that'll make it front-page news.

I need to rest my wrists and stretch the muscles in my back and neck that have tightened me into a hunched-over position in these last few hours. I'll be back.

OK, I've managed to get back on the raw image website, and I grabbed a whole bunch of the images that we were apparently looking at earlier. I just threw together this little animation, showing mostly Impact Targeting Sensor images, but moving at the end to some Medium Resolution Imager images. Now, I've probably dropped some frames, and these images are smaller than the ones the scientists get to use, but I have to say that this is pretty sweet as it is. I can't wait to see what the scientists produce!

Animation of the Deep Impact into Tempel 1

NASA / JPL / U. Maryland / Emily Lakdawalla

Animation of the Deep Impact into Tempel 1
This video was assembled from 36 images taken by the impactor's camera, and twelve taken by the flyby spacecraft's camera.

Just to make things stranger here, June Lockhart (of Lost In Space fame) just showed up.

I wandered into the auditorium a few minutes early to make sure I got a good seat. In the back of the room I bumped into my friend Trina Ray, a JPLer who is the head of the group that plans the Titan science on the Cassini mission. "I'm just lurking," she said.

Inside the room, on the left, are the press; on the right there are lots of those blue and red shirts we saw on TV. Feels like a wedding! Am I with the bride or the groom?

Seats are full now, more reporters are walking forlornly by with their laptops, looking for spots...

Ready for the triumphal press conference!

I just spotted Pete Schultz and Jessica Sunshine, heading up to the front row. There are Congresspeople and other Important Persons there but as far as I'm concerned they should be the stars! -- after the engineers and navigators who got us to this point, that is.

The panel consists of Andy Danztler, Rick Grammier, Keyur Patel (that's a new name on me), and Mike A'Hearn. We all applaud as they come out.

Mike A'Hearn's getting his bald head powdered again. Poor guy! We are laughing with him...I think...

Sorry for the delay, they seem to be having some technical problems. It'd be ironic if they could accomplish the Deep Impact mission but not get a press conference going!

OK, the inevitable joke has been made, to Rick Grammier. "Rick, you've got your next job coming, to get the audiovisuals working."

I think actually that the holdup is getting the images ready to go. If true, that's worth the wait.

They keep saying "30 seconds" and counting down -- and then something holds them up. Mike A'Hearn just joked that they may be serious about the 30 seconds -- but forget to tell us the minutes part.

OK, here we go!

They are smiling this time! Andy Dantzler reminds me of Colin Mochrie, of Whose Line is it Anyway? fame...

Elachi: "I am wondering if there is a comet up there that is wondering, 'what the heck hit me?'"

David Southwood is actually sitting here, from ESA...he gets applause.

Al Diaz: "Happy Birthday, America. It's great to be on the west coast when, for the first time, the fireworks started here. Let me congratulate the science team, for a great idea, and for having the persistence to make it happen."

Andy Danztler: "What a smashing success." He gets grudging laughter. "This has been quite a hit for NASA, quite a success for the team in general. A wonderful collaboration around the world, including the ESA Rosetta spacecraft. Just in cas you missed it, we have a picture of the impact. That is phenomenal. I'm trying to think of how to describe this, but I am just speechless."

Grammier: "I'm more relaxed than the last time I was up here, that's for sure. Just to give you status on the mission, we are minus one spacecraft, the impactor, it's been totally vaporized, as per plan." He compares the video to a still from the actual impact. "We didn't go through a single contingency." He shows video of his team. "I have a fun crew, what can I say?

He showed an animation from the impactor, and the still photographers in the room started shuttering away -- but the biggest roar as we went in was from the team members in the red and blue shirts. "I think, Mike, we provided you the science you wanted." A'hearn: "Yep."

Patel: "Wow." .. "Flyby is doing great. It came out of shield mode with not a bit of damage. Between the flyby and the impactor, we were imaging the same spot within only 50 meters, which is absolutely amazing." Shows an image: "This is just incredible."

A'Hearn: "As we were sending the images off to be prepared for this press briefing we were of course still watching the images coming down. There are many more spectacular images yet to be revealed.

"There's the whole comet. It's about 5 kilometers across, 7 or 8 long in this projection. But we're not seeing the full long dimension of it in this picture. This is a closeup image. It has a scale of about 7 meters per pixel. We've gotten the highest resolution images of a comet ever. The impactor was perfect. The flyby instruments also worked beautifully. We got tremendous spectra, really strong spectral features, great thermal spectra. The flight team has just completed most of its work, we are just starting our work now. Obviously it was a very big impact, presumably we have a large crater. Interpreting the ejecta cone is going to take a bit of time. There is lots of structure in it that is of interest to interpreting the nature of the comet. I look forward to the wealth of data that will take me to retirement."

Time for press questions.

A'Hearn: "We only have 10 percent of the data down. It was still a very large ejecta cone in the first lookback imaging, which was 45 minutes later than the impact. We've made some crude estimates of the amount of material but I think we're going to hold on to them until we've had a chance to think about them."

Hubble etc.? A'Hearn: "They observed a brightness increase of about 3 magnitudes. A few telescopes reported big increases in emission lines in the spectrum."

An Australian reporter just asked whether this mission could have been pulled off without the telescope in Australia, and everybody laughed. Grammier answered: "Obviously not."

Grammier: "Yes, we did have to bother, because as we were closing in, the comet was moving too, and we didn't know the exact size and shape of this comet. First ITM was 1.26 meters per second. Next one was 2.2 meters per second, and the third one was 2.3. After each one was done, then the next cycle would pick up to do the next AutoNav solution. Our confidence started increasing, not only as the images were growing larger and we knew we were dead on. but also the adjustments were minor. In the last 30 minutes we knew we were going to have a good day."

Was the plume big? A'Hearn? "I haven't had time to sit down with the cratering experts on my team, but clearly it rules out really porous structures where you tunnel very deeply -- the aerogel capture scenario. It rules out those structures without a doubt. It probably rules out a strength dominated crater, but I won't say any more than that."

Natural vs artificial outburst? A'Hearn: artificial one was "obviously a LOT bigger."

Was comet size or shape dramatically different from expectations? A'Hearn: "Since we didn't know what to expect, it wasn't surprising."

Patel: "It survived completely intact. Every subsystem was operating nominally." A'Hearn: "Given the quality of hte lookback images, the optics survived perfectly also."

I walked up to Pete Schultz after the press conference. "Did you get the big boom you wanted?" I asked him.

"Oh yeah," he said.

"Was it what you were hoping for?"

"Yeah. And what this tells us is, experiments work."

"Is that the lesson we should take away from this mission?" I asked.

"Damn straight."

Then I caught up with Jay Melosh (who never remembers me, but I can't blame him. I actually interviewed with him as a potential graduate student, way back when).

Anyway, I asked him if he was happy, and he most certainly was. "We expected to be surprised. I am gratified to be surprised."

 
See other posts from July 2005

 

Or read more blog entries about: mission status, explaining technology, comets, comet Tempel 1, Deep Impact

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