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What to expect when you're expecting a flyby: Planning your July around New Horizons' Pluto pictures

Posted By Emily Lakdawalla

10-03-2015 19:06 CDT

Topics: New Horizons, Pluto, Charon, mission status, Pluto's small moons

Note: A revised version of this post, "What to expect when you're expecting a flyby: Planning your July around New Horizons' Pluto Pictures (version 2)," is now available. Please go there for the most accurate information.

New Horizons is now closer to Pluto than the Sun is to Earth: 1 astronomical unit, or 150 million kilometers. A tiny course correction burn steered them closer to their goal today. As New Horizons begins to approach Pluto, there's a single question everybody keeps asking me: when will we get the first pictures? The trivial answer to that question is that we already have them. But as exciting as it is to know that New Horizons has sighted Pluto, a teeny dot wobbling among stars is not what people mean when they ask about New Horizons' pictures. What people want, of course, is the portrait photo, the one we're going to be seeing on magazine covers and in textbooks for years to come.

As New Horizons approaches, every image of Pluto and Charon that each instrument returns will be the best it has ever taken. They will be thrilling to see. But until mid-July, all the images will still be pretty small. In the days leading up to the July 14 flyby, with only one exception, all of the images that we will receive of Pluto and Charon will be lower-resolution than the best Ceres pictures we have received from Dawn to date.

Approaching Ceres

NASA / JPL / UCLA / MPS / DLR / IDA / collage by Emily Lakdawalla

Approaching a dwarf planet

These Dawn images of Ceres have similar quality to the best images that we will receive from New Horizons at Pluto through July 13, the day before the flyby. Only one image that New Horizons will return before the flyby will be higher-resolution than these.

In this blog entry I'll try to explain when we'll get the images that you're hoping for. First, the executive summary:

It's hard to get data from Pluto

Data will arrive on Earth in a series of downlinks. Downlink sessions can last as long as about 8 hours, but are usually somewhat shorter. Whenever New Horizons is downlinking data, it can't take new photos, so the downlinks get shorter and less frequent as the spacecraft gets close to the time of the flyby, when it concentrates on collecting as much data as possible. Because data downlinks are slow, there will be much less data downlinked than New Horizons has stored on board. After data is downlinked, it must be processed before posting online. How long that will take is not yet known.

On Sunday, July 12, New Horizons will transmit the last of its optical navigation data. These images will have lower resolution than the images we have already received from Dawn at Ceres. Then, on Sunday and Monday, July 12 and 13, there will be a series of four "Fail Safe" downlinks. These are designed to return a minimum set of data from all instruments, just in case New Horizons does not survive the flyby. A last downlink ending overnight Monday July 13, called "E-Health 1," will include one last pre-closest approach photo of Pluto.

Then there is a nail-biting 24-hour period of waiting while New Horizons concentrates on flyby science and does not communicate with Earth, followed by the much-anticipated beep of the "Phone Home" downlink on Tuesday night, July 14. Following closest approach, on Wednesday and Thursday, July 15 and 16, there will be a series of "First Look" downlinks containing a sampling of key science data. Another batch of data will arrive in the "Early High Priority" downlinks over the subsequent weekend, July 17-20. Then there will be a hiatus of 8 weeks before New Horizons turns to systematically downlinking all its data. Almost all image data returned during the week around closest approach will be lossily compressed -- they will show JPEG compression artifacts. Only the optical navigation images are losslessly compressed.

The transmission of the High Priority data set will be complete on July 20, and then image transmission will pause. For nearly two months, until September 14, New Horizons will switch to near-real-time downlinking of data from instruments that generate low data volumes (like SWAP and PEPSSI) while it transmits just housekeeping information for all of the rest of the data. No new images will arrive on the ground during this time.

On September 14, New Horizons will begin downlinking a "browse" version of the entire Pluto data set, in which all images will be lossily compressed. It will take about 10 weeks to get that data set to the ground. There will be compression artifacts, but we'll see the entire data set. Then, around November 16, New Horizons will begin to downlink the entire science data set losslessly compressed. It will take a year to complete that process.

What to expect, when

Here is a graphical summary of all of the LORRI data that New Horizons is expected to downlink in the two weeks surrounding closest approach. I used Voyager images of Jupiter and Saturn moons to stand in for Pluto, Charon, Nix, and Hydra: Ganymede for Pluto, Tethys and Rhea for Charon, and Janus and Hyperion for Nix and Hydra. Don't take the comparisons between the moons and Kuiper belt objects too literally -- this comparison is just meant to give you a sense of the scope of the near-encounter data set at a glance.

Simulation of the New Horizons Pluto flyby LORRI data set

Voyager images: NASA/JPL. Chart by Emily Lakdawalla.

Simulation of the New Horizons Pluto flyby LORRI data set
In the two weeks surrounding New Horizons' flyby of Pluto, only 1% of the science data that it acquires will be downlinked to Earth. This chart uses Voyager images of Jupiter's and Saturn's moons to stand in for the images that New Horizons' highest-resolution camera, LORRI, is expected to downlink in the summer of 2015. Visit for futher explanation.

Following is a complete list of all the planned downlinks of image data during the highest-intensity period around closest approach. The times given are planned downlink end times. Downlinks containing LORRI images, which should be released automatically, are in bold. It is not yet known how long it will take the pipeline to run that will send these images to the Web. When I find out more precisely how long it will usually take to generate images from the raw data, I will update this post. Also, the times and ranges of the images may change by as many as 7 minutes and 6000 kilometers as navigators update their knowledge of Pluto's position; I will update this post as necessary. Therefore, I do not recommend the copying and reposting of this text, because it will become out of date!

Note: A revised version of this post, "What to expect when you're expecting a flyby: Planning your July around New Horizons' Pluto Pictures (version 2)," is now available. Please go there for the most accurate information.

Sunday, July 12 19:40 UT / 15:40 ET / 12:40 PT: 7hr 5m downlink: Final optical navigation images

Monday, July 13 02:24 UT / Sunday, July 12 22:24 ET / 19:24 PT: 4hr 13m downlink: Fail Safe A

Monday, July 13 06:15 UT / 02:15 ET / Sunday, July 12 23:15 PT: 2hr 30m downlink: Fail Safe B

Monday, July 13 at 10:40 UT / 06:40 ET / 03:40 PT: 1hr 14m downlink: Fail Safe C

Monday, July 13 at 16:25 UT / 12:25 ET / 09:25 ET: 3hr 30m downlink: Fail Safe D

Tuesday, July 14 at 03:15 UT / Monday, July 13 at 23:15 ET / 20:15 PT: 52m downlink: E-Health 1

Wednesday, July 15 at 00:09 UT / Tuesday, July 14 at 21:09 ET / 18:09 PT: 17m downlink: Phone home

Wednesday, July 15 at 10:00 UT / 07:00 ET / 04:00 PT: 1hr 29m downlink: First Look A

Wednesday, July 15 at 19:25 UT / 15:25 ET / 12:25 PT: 6hr 54m downlink: First Look B

Thursday, July 16 at 04:24 UT / 00:24 ET / Wednesday, July 15 at 21:24 PT: 1hr 50m downlink: First Look C

Thursday, July 16 at 07:24 UT / 03:24 ET / 00:24 PT: 1hr 52m downlink: First Look D

Thursday, July 16 at 13:23 UT / 09:23 ET / 06:23 PT: 4hr 15m downlink: First Look E

Friday, July 17 at 16:33 UT / 12:33 ET / 09:33 UT: 3hr 15m downlink: High Priority A

Saturday, July 18 at 10:30 UT / 06:30 ET / 03:30 PT: 4hr 36m downlink: High Priority B

For the rest of Saturday and Sunday, downlinks include REX and LEISA data, with no LORRI or MVIC data.

Monday, July 20 at 16:03 UT / 12:03 ET / 09:03 PT: 3hr 15m downlink: High Priority G

After that, we must wait for September, when the downlink of the full data set will begin. But there will be plenty to explore in this first taste of the New Horizons data!

For even more detail on the images that will be acquired and downlinked during the near-encounter phase, you may enjoy this New Horizons team "Playbook".

Many thanks to Alan Stern and Kim Ennico for helpful comments!

See other posts from March 2015


Read more blog entries about: New Horizons, Pluto, Charon, mission status, Pluto's small moons


Petsas Chrys: 03/10/2015 09:45 CDT

I was wondering why there is not a set of orbits or multiple fly-by's planned. Is it because of speed/planet mass limitations or because of insufficient fuel of the spacecraft? So petty that we spent all those years and money for just so tiny science outcome.

ethanol: 03/10/2015 10:33 CDT

Fantastic post Emily! Petsas: New horizons will pass Pluto going over 14km/s. Not even Dawn, with its solar-powered ion drive, could kill that much velocity. A chemical rocket capable of such a burn would be massive, and would have required a launch vehicle much larger than any that exists today. But no worries! New Horizons has been designed from the very beginning to collect lots of data in a very short period of time. It won't deliver global coverage at the highest resolution, but it will revolutionize our understanding of Pluto, once they get all that data back...

Messy: 03/11/2015 11:10 CDT

Emily! Petsas: As my parents used to say: It's better than nothing. The simple fact is, is that NASA didn't WANT New Horizons in the first place. When Nixon cancelled Voyagers 3 and 4 back in 1970, NASA gave up on ever going to Pluto. It was too expensive and would bring back too little data. However... It was considered the 9th planet, and professionals and enthusiasts everywhere wanted the mission to get good data on every single one of the major planets. In the '80s, NASA commissioned a poll of scientists s to what kind of missions they wanted done, A Pluto mission was by far and away the most wanted and considered the most important. The High mucky-mucks at NASA were shocked, but there it was. They had to give the people what they wanted, and what they wanted was a mission to Pluto, to basically complete the grand tour taken by Voyager 2. Considering the cowflop that flew over DAWN (which was cancelled while the actual spacecraft was being constructed), it's a miracle that New Horizons ever got off the ground. I'm pretty sure that had Pluto been demoted before it was launched, it never would have. New Horizons is the last probe of it's kind. A 1960s-70s style flyby reconnocense mission. It's the final in a series that began with Luna 3 in 1959. The final new world. the Solar System as we knew it in 1960 will now be complete.

crazypete: 03/11/2015 02:24 CDT

Excellent information, I have been looking for a timeline so that I don't have to obsessively refresh the JPL new horizons page. Which I'll probably end up doing anyhow.

Petsas Chrys: 03/11/2015 02:50 CDT

Thank you both for the usefull information. By the way i forgot to praise Emily for this rich article!

Ed: 03/11/2015 03:13 CDT

Thanks for the excellent post, Emily. This is the precisely the type of information I'm interested in. I'm wondering whether, if a lossy pic shows something particularly interesting, might the lossless version be sent "immediately", or ahead of schedule. I can't imagine either the software not providing this capability (I'm a software engineer) or the PI's being inflexible if a clearer view is desired for a particularly intriguing image. [Just how big need an obelisk* be, to be clearly seen? ;) ] I've been following New Horizons since before launch. I'm stoked. Thanks again! *I'd much rather find an obelisk, than Puppet Masters!

Emily Lakdawalla: 03/11/2015 05:33 CDT

I'm glad you all enjoy the article. NH is flying past Pluto at a relative speed pretty similar to the Voyager encounters. The difference is that there is no giant planet that can be seen well from far away -- there is only a thing that is smaller than 8 solar system moons, and another thing that is half that size. While researching this article I found that the Voyager 1 approach imaging of Ganymede had a very similar cadence (in terms of how much the disk grew from image to image) to the plans for New Horizons approach imaging of Pluto; overall Ganymede from Voyager 1 really was a great match for NH plans at Pluto. Keep in mind that Ganymede is more than twice the diameter of Pluto!

Firelake: 03/14/2015 03:54 CDT

Thank you Emily for this elegant overview. Often, articles miss this part making it difficult to see the big picture and overall purpose with the many missions. Sometimes, you'll have to google a lot to get this. A question regarding the Pluto mission: Even though Pluto is not that big I was rather baffled reading in your article that "only" in reality low resolution pics are planned. In these UHD times I'd expect more like 2.000 x 4.000 pix or the likes of the planet. Couldn't the optics have been upgraded or the fly by closer to obtain this?

Ed: 03/14/2015 12:54 CDT

Firelake: I'm no expert. However, A) I suspect New Horizons will get as close to Pluto as can be "safely" done. Also, regardless of how close it gets at closest approach, most images will be from further away. B) Depending on the lens and distance to target, there are "analog" limitations on image quality. At some point, increasing digital resolution (pixel density or depth) is pointless. The HD images you're used to are of targets far closer to the camera than will be Pluto to New Horizons.

Ed: 03/14/2015 01:10 CDT

I'm curious about the difficulty in travelling outside the ecliptic plane. New Horizons will reach Pluto just as Pluto is very close to the ecliptic plane. A space vehicle can only get a gravity assist in the direction of movement of a large body (i.e., pretty much limited to a vector parallel to the ecliptic plane). Pluto crosses the ecliptic plane only about once every 124 Earth-years, of course. I'm wondering whether (given current technology), the visit to Pluto is taking advantage of an opportunity that occurs only every 124 years? Would it be much more difficult to visit Pluto 50 Earth-years from now (yes, even the distance component parallel to the ecliptic plane would be greater, but that wouldn't be a "big" problem; I'm talking about delta-v in the "z" axis, if we're "looking down" at the solar system). Are we taking advantage of a "rare" opportunity?

ethanol: 03/15/2015 03:37 CDT

Ed: While it is nice that Pluto is crossing the ecliptic, I don't think it was necessary. Gravity assists, particularly from gas giants, afford ample opportunity to cheaply change orbital inclination. Voyager 1 aimed well out of the ecliptic after passing Saturn, and then of course there was Ulysses, which used Jupiter to enter a polar heliocentric orbit. So it's probably more like a once / five-year window, because Jupiter has to be in the right place for the slingshot.

scottherman: 03/25/2015 08:06 CDT

Thank you so much, Emily, for this incredible article. It was exactly the information needed to understand what will be happening. Compliments on the level of detailed research.

jim: 03/27/2015 02:33 CDT

No green filter? Does that mean we won't get any true color pictures? What were they thinking? Can you explain why a probe that's 3 billion miles closer to Pluto than Hubble can't take better pictures? Are the camera lenses that bad or is Hubble just really good?

quasito: 06/06/2015 02:31 CDT

Thanks Emily for your thorough explanation, just what I was looking for!

SciGuy: 06/23/2015 04:25 CDT

@Jim "No green filter? Does that mean we won't get any true color pictures?" All color pictures are approximations to one degree or another. Even your eyes don't see the 'real' color spectrum that exists, but instead see a distorted version of it because the cells in your eyes are only sensitive to 3 colors. "What were they thinking?" They were thinking it would be more valuable to determine mineral types with infrared filters than to image a surface that isn't expected to have very much green on it. "Can you explain why a probe that's 3 billion miles closer to Pluto than Hubble can't take better pictures?" Hubble is a telescope the size of a school bus. It is 95 inches in diameter and weighs 24,000 pounds. LORRI is the New Horizons telescope and is 8 inches in diameter and weighs 18 pounds. It could fit in a large backpack. They are very different instruments. Take a picture of someone standing on top of a mountain from 50 miles away. Now take another from 25 miles. Can you see the person? No. New Horizons is still a long way away, and Pluto is very small.

wilderness: 07/14/2015 09:31 CDT

To elaborate on SciGuy's answer: There's enough information stored within the red and blue channels to extrapolate the green. The tricky part is separating that info. With a known light source, known surface properties and a lot of processing, the natural green can be interpolated into the final image. Every piece of equipment adds a critical burden on constraints like launch schedule, budget, weight (launch thrust), instrument operating energy, and observation schedule (hard mounted cameras limit experiment concurrency). NH was rushed to launch to make the small window where the planets were aligned so we could get there in (unbelievably) under a decade. Including another camera was not only unnecessary but we wouldn't even be at Pluto yet if we had. While it takes them a lot of effort to process the green back in, it was a small price to pay to make way for more scientifically valuable instrumentation like the IR spectrometer - and they did it while fully preserving the public interest of natural color images. It's really quite genius.

kenc3dan: 07/14/2015 12:53 CDT

Grayscale=R+G+B (to some extent) If you know R and B, then you can use the grayscale to reconstruct the missing G. Does that sound right?

kenc3dan: 07/14/2015 12:56 CDT

Yeah, that color looks wonky to me. Kinda flat. Then again, I've never seen Pluto. :-p I just bet the images to come will look substantially different.

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