Postcards from Pluto

picture taken by Rayna Tedford

Back in January, the folks who built the Venetia Burney Student Dust Counter (SDC) for New Horizons got together for a reunion at SwRI Boulder, where I work.  I'm not involved with the SDC, its operation or the science that comes out of it. So it's awkward to admit that I'm also not entirely on top of what the SDC is up to. So I thought I'd drop by the reunion and learn a little more.

At the reunion, there were talks about what the building process and review process was like, as well as talks about the science from the instrument so far.  Then we went out for snacks.

The eponymous students were a mix of graduate students and undergrads from the University of Colorado at Boulder.  Most missions are designed with an outreach component geared toward schools, but the New Horizons SDC was the first NASA planetary EPO program to have an instrument that students built and operated themselves on a real mission. About 30 students were involved in designing, building, and testing SDC.

The students were subjected to the same standards and the same NASA reviews of the other instruments.  They definitely rose to the challenge:  the SDC was the first instrument finished, and the final cost was closer to the initial estimate than any other instrument for the mission.

Since launch, there's been always been a grad student operating the SDC, taking data and reporting to team meetings- in the nine years since launch, three such grad students have been involved.  Unlike most other instruments, which shut down whenever the spacecraft entered hibernation, the SDC has been taking data throughout New Horizons' nine-year journey.  

New Horizons' distance from the sun allows it to probe areas where no dust measurements have ever been made.  The now-silent 1970s space probes Pioneer 10 and Pioneer 11 both had dust counters, but Pioneer 11 only made measurements inside of 10 AU, while Pioneer 10's measurements went out to 18 AU.  No more measurements could be made after 18 AU because the gases used in the instrument to detect impacts froze.  An AU (Astronomical Unit) is the distance between the Earth and the sun.  For reference, Pluto will be at around 33 AU from the sun at encounter time.  SDC has already made measurements from 1 AU out to 32+ AU, a record!

The SDC can measure the rates and masses of particles that impact its detectors; the number of particle strikes is used to estimate the density of dust in the Outer Solar System.

Due to something called Poynting Robinson drag, particles can be pulled inwards toward the sun.  Therefore, some dust particles seen by the SDC must have been from farther out in the Solar System-- particularly from the Kuiper Belt.

Right now, there's another dust instrument taking measurements far beyond Earth.  This one's on the Cassini Saturn orbiter mission; it's called the Cosmic Dust Analyzer (CDA).  The CDA has an ability that the SDC does not-- it can tell the direction the detected dust came from.  Using that information, the orbits of incoming dust particles can be calculated.  However the CDA has one huge disadvantage, it's "stuck" in the Saturn system (don't feel TOO bad for it), while the SDC is traveling out and away.

From probing parts of the outer solar system before and beyond Saturn, the SDC team was able to predict how much the Kuiper Belt dust CDA sees. The CDA measurements match SDC predictions, which is pretty cool.

While SDC is a trailblazer, NASA has recently expanded opportunities for student instruments following its success on New Horizons, and now a bunch of schools have started programs to build instruments for NASA space missions.)

And what happened to the SDC alumni?  They're in their 30s now and many are now married with kids (some of whom came to the reunion).  I found out the evolution of five former SDC students at dinner.

1.  One woman joined the project as an undergraduate as a fluke.  She toured the Laboratory for Atmospheric and Space Physics (LASP) at CU, and the guide mentioned they wanted résumés.  She sent hers in and the rest is history.  These days she programs flight software for space instruments.

2.  One man is a project manager and works on wind power.  While what he is working on is very different from making instruments for space missions, he learned lots of applicable management lessons from working on the SDC project.

3.  An electrical engineering grad student who wasn't at the reunion recently decided on a different path, and now lives in Thailand, where he is a monk.  Some SDC alums still keep in touch with him on Facebook.

4.  Another woman is very doing similar work to what she did on the SDC even today.  Back in the day, she tested the SDC detectors as an Aerospace grad student.  More recently, she worked on the detectors for the LADEE mission.

Picture from the Colorado DMV.

I'm super excited to report that the two KBOs we are deciding between are officially called 2014 MU69 (PT1) and 2014 PN70 (PT3).  Those are a mouthful of random numbers and digits, huh?  That's why we call provisional designations like these "license plates".   My first thought was that I should get someone on our team to have this as their actual license plate.  I'd do it myself, but I don't own a car.  Sadly, CO license plates have a max of seven numbers.

They are also the first official names for our KBO targets, which means you can go to JPL's Horizons, type in those names, and learn where to look for the objects in the sky from any location in the Solar System.  You know, if they weren't among the dimmest objects discovered in the Kuiper Belt and could be easily spotted in ground-based telescopes.  

Once one submits positions of an object from more than one night to the Minor Planet Center (MPC), names are immediately assigned.  So, why did this take so long for our KBOs to get designations from the MPC?  Well, this one's our fault really.  We wanted to send the MPC our very best orbit positions, not the first ones that came out of our computers.  Or the second ones. So we waited until we had results that we thought were super reliable.

Since we didn't have submitted positions done by the announcement of the discovery of the two objects, we had to come up with alternate names.  Internally, PT1 had been given the designation 1110113Y, a name that has zero meaning outside of the KBO search team.  The name makes more sense if you think of it as 11-1-011-3Y . We called it that because it was discovered on HST visit pair 11-12, chip 1 (of 2) and it was the brightest on shift stack 011, though we could see it on many stacks (I explained our shift-stacking method here.  At one point last summer, I got really excited because I thought I discovered a KBO, but nope, it was object 1110113Y again, popping up in a different stack.  Nope, hopes dashed in 30 seconds flat.).  The last two numbers are just alphanumerics because it was one of hundreds of potential sources that Marc Buie's program picked up per shift stack that he had to vet to determine if it was a real object.  Using A-Z in addition to 0-9 gives us 1296 options for a 2 digit number, versus 100.  

Among, us, perhaps Simon Porter was the only one who had the whole string memorized.  We all called it object 11.  It was really weird reading posts online and seeing people talk about 1110113Y, when none of us called it that in our own discussions.  There was also object 7 (0720090F, found in the pilot), object 45 (4510067S), e3 (e31007AI - we switched to hexadecimal for the tens digit after visit pair 99-a0), and finally g1 (g12000JZ).

We really didn't want to be calling anything "object 11" in the news.   We never had 11 objects and the "visit pair 11 and 12" concept just took too long to explain.  So we needed alternate names, and Xena, Santa and Easter bunny were not our style.  We knew we'd be getting the license plates eventually; so we needed something ... forgettable.  Saying "remember that Xena thing that was in the news?" to my family and friends so they'd know what I was talking about when I was trying to discuss Eris was bad enough. We didn't want to unofficial names to have a life of their own.

By the fall, we had 11, e3 and g1 left as targetable in the fall, so how about PT1, PT2 and PT3-- Potential Targets 1, 2, 3.  And those names stuck with us so much that we stopped using 11, e3 and g1-- I've been asked if PT3 was e3 or g1 more than once.

So here are our names: 0720090F = 2014_MT69 1110113Y = 2014_MU69 (PT1) e31007AI = 2014_OS393 (PT2) g12000JZ = 2014_PN70 (PT3)

The minor planet center gives us these names based on when the object was discovered (they explain how here).  

Here's how it works.  I did not invent this system, so do not blame me for it.  Objects 11 and 7 were discovered in the 12th half-month of 2014, designated "M" (because they skip I and Z).  So the first 25 new objects (because they just skip “I” now) found from June 16-30 are 2014 MA, 2014 MB, ... 2014 MZ.  The next 25 are 2014 MA1, 2014 MB1, ... 2014 MZ1.  So by the time we sent our positions in, they'd been through the truncated alphabet 69 times already. Thus, 2014 MT69 and 2014 MU69, are consecutive designations.  If we sent our designations in earlier or later, we might have gotten nicer numbers (I've also made all the jokes about the designations already, so you don't have to).  Boy, July 16-31, 2014 (half month "O") was a busy, busy month, I wonder what was going on then.

Why is object 45 not on the list?  Well, you only get a name if you see an object on more than two nights.  We never followed up on it because we knew immediately that New Horizons couldn't reach it, even based on what little we know of its orbit.    It would have been dishonest to request Hubble time for an object what we knowingly couldn't reach.   Hubble time is very limited, and wasting the orbits that we had been given for following up an object for the sake of chasing it, would have jeopardized our ability to get more time to characterize the good objects. Object 7 was a different story.  Our first calculations had object 7 as a more reachable target than object 11, but we weren't able to rule it out without follow-up observations.

2015 March 14

Next Exit: Pluto!

Explanation: After more than nine years in space, on a voyage taking it farther to its primary destination than any mission before it, NASA's New Horizons spacecraft is within one astronomical unit of Pluto - meaning it's closer to Pluto than the Earth is to the Sun. Speeding along at nearly 33,000 miles per hour, New Horizons sailed past its last symbolic deep space mile marker at about 5:20 p.m. EDT on March 10.

Happy New Year!  Welcome to 2015, the year of Pluto!  It’s hard to believe that we’re so close to encounter time!  Things are going to be picking up quite a bit around here.

  So, today I just got back from holiday break with my family back east and found a nice holiday present from my boss, New Horizons Principal Investigator Alan Stern sitting on my desk.

  The note says that it’s a Pluto stress ball, sold at Lowell Observatory in Flagstaff, Arizona (where Pluto was discovered in 1930 and well worth a visit).  Now, I know complaining about Christmas gifts is pretty rude, but this is not a very accurate depiction of Pluto.  Let’s talk about why.

  Firstly, the stress ball is the wrong color.  While we can’t yet see Pluto clearly, indirect mapping and spectroscopy tell us that it’s reddish in color and has bright and dark patches.  This stress ball is gray and the same color and brightness all around, like, well, Charon.

  The stress ball is also covered in craters.  We don’t know if Pluto has craters or not. It might have some, or there might be frequent resurfacing, and Pluto might be full of mountains, canyons and plumes.

  There are three major types of craters: simplex, complex and multi-ring basins.  Which one you see depends on how big the thing that crashed was.  Small impactors make simple, bowl shaped craters.  If the impactor is big enough, the crater will be more pie-pan shaped and there will be a peak in the middle, and that’s a complex crater.  A humongous collision will make a multi-ring basin, like Orientale on the Moon.  All of the craters on the stress ball are simple, and some of them are, well, a bit big to be simple craters. 

  In general, the simple craters are about 5 times wider across than they are deep, and complex craters and basins are even shallower. Based on what we've seen on moons of Saturn and Uranus, we predict that Pluto's craters would be 10 times wider than they are across before they get shallower too.  Based on highly scientific measurements from sticking my pencil eraser in some crater and measuring them with the ruler on my protractor, I’ve determined that these craters are only 3-4 times wider than they are deep, in other words, too deep!  Making craters deeper requires different surface properties, and so perhaps Pluto and Charon are actually made of squishy foam?

  The craters are also very well preserved.  Alan, fellow postdoc Simon Porter and I have written a paper predicting what types of craters on Pluto and Charon we’ll see and what different scenarios will tell us about the makeup of Pluto’s surface and the population of objects available to hit them. 

We find that escape erosion (the idea that Pluto is losing its surface gradually to space) and relaxation (due to meltier nitrogen at Pluto temperatures) might cause Pluto’s craters to either shrink, flatten or disappear altogether in just a short amount of time.  This won’t happen on Charon because it’s covered in rock-hard water ice (I explain why the two surfaces are so different here).  If something hits Charon and takes a big chunk out of it, unless there’s tectonic activity on Charon or something, that big hole in the ground will be there forever.

  Actually, the idea that there’s a big chunk missing out of Charon isn’t unheard of.  In 2005, Charon passed in front of a bright star (aka a stellar occultation), and folks from the MIT-Williams occultation group caught it from several sites (I used to work for this collaboration, but this was before my time). There were some anomalies that were consistent with either a timing discrepancy between measurements from the SOAR and Gemini Telescopes (check out Figure 2), or there’s a large, disfiguring crater on Charon that makes it not otherwise round.

Personally, I think it’s a timing discrepancy, but we’ll be able to track where that spot was on Charon and learn the answer soon.

Hey guys,

Alan and the post doc crew (including me) will be doing a Google Hangout from 4-5 pm EST on Wednesday, December 10, hosted by Fraser Cain.

You can hear what’s happening now that New Horizons is out of hibernation and get any questions about the mission answered.  I’ve never done one of these before, should be interesting.

The Goldstone 70-m antenna, one of three antennae that are part of the Deep Space Network.  Source: NASA

Wake up, New Horizons!  This Saturday, December 6, New Horizons will come out of hibernation for the last time before its encounter in July 2015.  Throughout the cruise, New Horizons has been put in and out of hibernation, which prevents the electronics from aging as quickly during the nine years they’ve spent in space so far.  It won’t return to hibernation for at least the next two years.

There will be some events going on for the wake-up: the mission will be live-tweeting the wake up. Once we hear from the spacecraft, an announcement will be made to the media, and there will be a wakeup song, .  The Planetary Society’s Emily Lakdawalla has a write-up on the wake-up and the encounter.  The Planetary Society is also hosting a live wake-up event, on Saturday December 6 from 9 to 10 PM EST. 

While the folks at Mission Operations (MOps) at the Johns Hopkins University Applied Physics Lab (APL)  will be testing the spacecraft over the next month, I don’t have any duties related to the wake up as a post-doc on the science team.  January 15, 2015 marks the beginning of Approach Phase 1 (AP1), and the first approach science.  Even though we will take more detailed measurements during Approach Phase 2,  I will be using some of these early AP1 navigation images taken by the LOng Range Reconnaissance Imager (LORRI) to continue making a solar phase curve for Pluto.

Last week was the 46th Annual Meeting of the Division for Planetary Sciences.  The meeting was held in sunny Tucson, Arizona, which was fantastic because the weather was nice and warm all week. The weather in Boulder was (and still is) rather frigid, so I'm not sorry to have missed the worst of it.

At DPS, planetary scientists gather to present the latest Solar System and Exoplanet research.  I presented a poster detailing efforts to measure the Solar phase curve of Pluto using New Horizon's LOng Range Reconnaissance Imager (LORRI).  It's still a work in progress, and the data we will get during Approach Phase 1 (starting in January!) will be needed to complete the project.

My poster along with everything Pluto was discussed on Thursday.  Pluto presentations covered all aspects of Pluto science from occultation measurements of the atmosphere, to ultra-high resolution Pluto spectra, to new estimates of the size of Pluto (gotta get the betting pool done before New Horizons answers the question once and for all) to laboratory work on the ices thought to cover Pluto's surface.  

I also got my first chance at monitoring an oral session.  This means I introduced each speaker, and made sure the the talks fit into their 10 minute slots and began on time.  Keeping talks on schedule (no earlier no later) is especially important because three oral sessions were held simultaneously and many people like to jump from one session to the other to hear particular talks on different topics.  While I did have to come up on stage because people went over time, it was never by more than a minute and a half-- so I did not have to resort to the drastic, Miss-Sweetie-Poo method of schedule keeping. I was surprised how nerve-wracking moderating talks can be. 

While the formal scientific program is useful, the chance to meet collaborators face to face is just as valuable.  I ate lunch with the MIT occultation researchers I hadn't seen since last DPS, I posed in the group photo of the New Horizons KBO search team, I got my software problems debugged in minutes in person with someone who would have ordinarily have done it via many back and forth emails from South Africa, and had a face to face New Horizons breakfast meeting that would have normally been conducted over the phone.  I also got to hang with some grad school pals that I've missed terribly.

Hi ddbeck,

PT2 and PT3 are more desirable than PT1 simply because they’re brighter.  Brighter means bigger, which means more science.  Brighter means we can see the object sooner with LORRI.  Brighter means the residuals on orbit fits will be smaller, and we will waste less fuel targeting the object and correcting our course.  However, we do not have enough information yet to know if either PT2 or PT3 will be reachable.  PT3 looks promising and PT2 is still possible, but not promising, and that’s the main purpose of our follow-up observations at present.  We discovered PT2 and PT3 over a month after finding PT1, and the time between the first and last observations (“arc length”) is the major factor that dictates how well we can predict an object’s orbit.

The encounter with PT1 would also happen during the winter.  The sun will interfere with communications only for a few days in January (not an encounter killer at all, but still sub-optimal). We could avoid that problem by going to the other objects.  PT3 would have a summer encounter.

We will be following up with all our objects with Hubble, but planning for next year hasn’t happened in earnest.  This week, we just started to get our last set of observations on these objects until spring.  Next summer, when the conditions are most favorable, we plan to try to detect these objects from the ground, but it will take a lot of image stacking and we don’t know if we can do it.  We’ll probably try with some of the big telescopes used for ground-based searching, like Subaru, Gemini and Magellan.

As for physical characteristics, another binary would be great (we can use Kepler’s laws to find the mass of the primary), but none of our potential targets appear to be binary.  That’s not a surprise—these objects are at the limit of detection.  A smaller body orbiting body would be beyond that limit.  I’m told a fast rotator might make imaging more difficult, so we’d like to try to get light curves of these guys. We’re going to try to get colors on the object, but I’m not sure if we’ve decided if we would prefer to see a KBO with an unusual color or a typical one (red, for this type of object).  The team still has more to talk about here.

Even if one of the brighter potential targets turns out to be reachable, we might just go with PT1 anyway.  We’re interested in the idea of looking at some of the KBOs the search team discovered (but we can’t reach) at their closest approach to the spacecraft, and conserving fuel will allow that to happen.

Hi Starsanshit,

I don’t think I have gone on the record with my personal preferences for Solar System nomenclature.  There’s some stuff in my notes talking about the naming procedures for a future blog post on the KBO search, but I might as well explain small body names now. 

The tl;dr answer is that Solar System objects get a temporary name that will be replaced by both an actual name AND a numerical designation, assuming it’s not “lost” to science.

Picture, if you will, the little girl from the taco commercial saying “why not have both.”

Having both is great.  Actual names are memorable: Makemake, Eris and Haumea are much easier to tell apart than 136472, 136199 or 1346108.  On the other hand, the numbers are easier to enter in a computer, find in a list, and they give you an idea how recently the object was found.

However, before an object gets a number or a name, it gets a provisional designation.  These have the year the object was discovered, the discovery half month, and the order it was found during that month.  You can find more detail about the process here.  Sometimes, you will come across older papers that have 2005FY9, 2003EL61 and 2003UB313 instead of Makemake, Haumea and Eris.

After a new object has been observed over the course of several years, it gets its number and the discoverer can propose a name. 

Finally, I can say that the New Horizons team has found three possible post-Pluto encounter targets!  I'm working on a post with more detail, but meanwhile, Emily Lakdawalla over at Planetary Society wrote an excellent article about our new objects (I think she said half of what I was planning to say anyway).

Meanwhile, if you have any questions about the search or our new objects, I would be happy to answer them!

Reminder, our Reddit AMA is at 1 PM EDT today.

Here's our link.  You need a reddit account to ask questions, but you don't need an email.  Reblog and spread the word!

http://www.reddit.com/r/IAmA/comments/2igklm/hi_i_am_alan_stern_head_of_nasas_new_horizons/

We’re doing an AMA on Reddit!

Next Monday, October 6 at 1 PM EDT, along with PI Alan Stern, and postdocs Kelsi Singer, Simon Porter, Alex Parker and Jason Cook, we’ll be answering your questions about the mission, Pluto and New Horizons.

This is one of the coolest serendipitous things to come out of the Hubble Space Telescope search for a post-Pluto encounter target for New Horizons.  See the spiral little galaxy hiding in the background?  That galaxy is on the other side of the Milky Way, invisible from the ground.  However, because HST gives us such high resolution views of stars, we can see between the mess of stars that make up our galaxy, through the other side, and get this very rare view!

Want to know how many days until the Pluto encounter AND keep all your mission news in the same place?  We’ve set up an outreach website on seeplutonow.com (easy to remember), and you can find links to PI Alan Stern’s Twitter, the New Horizons Facebook page, this Tumblr, the official JHUAPL site, as well as the Pluto Picture of the Day!

Announcing the Pluto Picture of the Day!  You can get your daily dose of Pluto at www.boulder.swri.edu/ppod, starting September 1 or at plutopod.tumblr.com.

 Here's a sneak preview: