alan stern

Hi, I am Alan Stern, head of NASA’s New Horizons spacecraft on its way to explore Pluto this year. Today is the anniversary of Pluto discoverer Clyde Tombaugh’s birthday back in 1906. Ask us anything about plans for the Pluto encounter and the history of Pluto’s discovery and exploration!

Hello Reddit. We’re here to answer anything about plans for NASA’s New Horizons mission Pluto encounter and the history of Pluto’s discovery and exploration. The mission’s closest approach to Pluto will occur on July 14th, 2015, but encounter operations have already begun!

Proof: – c.f. Alan Stern’s Wiki Page:

We are:

  • Dr. Alan Stern: Principal Investigator of New Horizons
  • Dr. Curt Niebur: NASA Headquarters Program Scientist for New Horizons
  • Dr. Cathy Olkin: Director of Office of the PI, Deputy Project Scientist, Co-PI on Ralph Instrument, Mission Science Team Member
  • Dr. Leslie Young: Deputy Project Scientist, Pluto Encounter Planning Lead, Mission Science Team Member
  • Dr. Marc Buie: Kuiper Belt Object Search, Hazard Analysis, and Mission Science Team Member
  • Dr. Michael Vincent: Payload Systems Engineer
  • Dr. Kelsi Singer: Mission Science Team Postdoctoral Researcher

The New Horizons spacecraft is about to flyby Pluto, 85 years after Clyde Tombaugh discovered Pluto, working at the Lowell Observatory in Flagstaff, AZ in 1930. Humankind is about to get high-resolution pictures and many other kinds of data on Pluto for the first time, and we want everyone to share in our journey of discovery!

Some good Pluto and New Horizons resources to read are:

What’s the future of communication for long range interstellar craft? With my small amount of reading I’ve done, it looks like New Horizons uses X-Band[1] and will only get 1kbps when it’s as far out as Pluto.
What’s next on the horizon as we get further out and have more bandwidth requirements?

This is Michael Vincent. The next step in higher rate communication at long distances is laser comm. Instead of sending a broad beam of X-band energy, send a very focused light, preserving a lot of the power. Take a look at the demonstration NASA did with laser comm to the moon:

How easy is it to aim the Earth from Pluto shooting a laser beam?

Michael Vincent: Not easy at all, and we don’t have laser comm on New Horizons. The first demonstration was Earth-to-moon, and that was successful. The next step is Mars.

How much faster laser communication could be? (with the same energy) Are we taking about orders of magnitude?

Michael Vincent: 10-100 times faster!

Is the craft still being controlled or just floating along its original trajectory? Or has it changed course due to unforeseen circumstances?

We’re on a trajectory to Pluto that only needs corrections to home in. We’re on original course.

How visible (to all instruments on board, not just cameras) do you expect Pluto’s atmosphere to be?
What are you personally hoping to find the most?

This is Michael Vincent: The short answer is almost all the instruments can play a part. Long answer: we are going to be imaging clouds with LORRI and MVIC (the “cameras”). With Alice, we are going to look through the upper atmosphere by tracking the UV light from stars we are looking at as we are moving (like looking at the Moon through moving clouds). Similarly with REX, we are going to be looking at the lower atmosphere by having the DSN send us a signal at X-band, and have REX record how that signal wobbles through it. We can even “sniff” the atmosphere with our in-situ plasma instruments PEPSSI and SWAP.

Will New Horizons’ data about Pluto’s atmosphere provide enough information for scientists to determine whether that atmosphere (at least some of it) is present during Pluto’s entire 248-year orbit around the Sun?

Leslie Young here. Three of here at the reddit (me, Cathy Olkin, and Alan Stern) have all worked on how Pluto’s atmosphere varies over its season. New Horizons will give a highly detailed snapshot which can be used to understand decades of telescopic observations and to fine-tune computer models. These all together will give us a much better understanding of how Pluto’s atmosphere varies, and how similar atmospheres vary on Triton or other volatile-covered Kuiper Belt objects.

When do you think the LORRI pictures will come back that will turn Pluto and Charon from astronomical objects into geological objects?

A few weeks before the closest approach on July 14th should be the transition between geological object and astronomical object :). Pluto is already not a point source (a few pixels across – new pictures will be released later today!) and a few weeks before we will start being able to make out the albedo patterns, and then actual geologic features as we get closer and closer! ~Kelsi

Just to reiterate, here are the new images 🙂

Have you compared the expected data volume from New Horizons’ Pluto encounter to other flyby missions? How does it compare to, say, Voyager 2 at Uranus or Deep Impact at Tempel 1?

That would be a great comparison to do, we haven’t yet though :P. ~Kelsi

What programming languages are you using? What kind of tools?

We have software tools for different purposes including helping to analyze the science data, checking the sequences of commands that we send to New Horizons to take data, and managing the downlink of the data. We have tools written in IDL, python, C.

Who gets to name geological formations that New Horizons discovers? Do you already have a list going?

We do. And yes, we’re working on that, no news for a while though….

Is the surface of Pluto really as colorful as shown in the Hubble photos, or is that an artifact of the digital processing?

The colors you see in the Hubble maps are as close to real as I could do. There’s a range of color from neutral and bright, red/brown colors, and black. It’s going to be very interesting to see if all that work was right or not. (Marc Buie)

So we will see colour photos too? I’m often in doubt if pictures of non-planet bodies are even in colour or grey scale because the objects are, you know, mostly grey scale.

We will be taking color pictures. The big moon, Charon, will be mostly just shades of grey. Pluto really will have different colors on the surface. We just want to know how the colors relate to different geologic regions. (Marc Buie)

Given the extreme range you’re dealing with, what is the maximum data rate available to you via the DSN? What frequency and modulation are you using, and how did you decide on a balance between bit error rate and bandwidth?

Michael Vincent: The typical rate we can downlink at is 1kbps. Just a trickle, really. There are a couple tricks we can play, though. First off, we can transmit with both our transmitters at the same time. That can nearly double our rate. Also, as the DSN station looks higher and higher in the sky, it gets less thermal interference from our own atmosphere here on Earth. At maximum elevation angles, we can get almost twice the data rate again. So, the maximum rate we downlink at from Pluto is 4kbps.

Thats an almost unbelievably high data rate considering the distance. As for being able to double the data rate at high elevation angles, does that mean that the spacecraft is programmed to change its transmit rate throughout a pass? And if so, thats incredible that even with light delay and the planet spinning (and what I assume is very very small half power beamwidths) that the data rate can still be so high with a decent link margin.

Michael Vincent: Thankfully, all the geometry is known ahead of time, so we do program the spacecraft to “rate step” through the pass. Our receiver is sensitive enough to lock to a signal as low as -160 dBm, though our commands are usually received at -120 dBm. That is what you get when you use a DSN antenna almost as big as a football field, and transmit at 20 kW.

What will New Horizons be tackling after you’ve finished with Pluto?

This is Michael Vincent: We are going to be spending a long time downlinking the goods for sure. After that, we have identified two potential Kuiper Belt Objects if we get an extended mission approval.

Will these potentially be any of the other 3 already known dwarf planets out there, like Makemake, Haumea or Eris?

Our flyby targets after Pluto are all much smaller than dwarf planets like Pluto and Eris, etc.; they are specifically desired to be the building blocks of dwarf planets, so objects 30-50 km across.

We won’t get close to any of the other dwarf planets. (Marc Buie)

What is the average turn around time for a raw image from LORRI? That is, how long from the time you get an image until it is released to the general public? Also…How long until we get some new pics?

There are several aspects to this. These include when the downlink is planned (can be up to weeks or months after the image is taken), then 4.5 hours or so to get the data to the ground, and then same day image processing by our computers. Following that we decide which noteworthy images to release.On a typical day now, zero to one or two images come down. Watch for an image release today.

Will there be a raw images page like some missions (ex, Curiosity) have? Where images just get dumped as they come in? Some of us are very impatient for any kind of Pluto pics.

There will be!

What’s your day to day like?

We’re all incredibly busy. We have mission sims, encounter planning, dat analysis, software tool building, and outreach activities to keep us busy, and it does, usually 7 days a week.

Does the Kerbal Space Program count as a mission sim?

We have mission simulations of different kinds. We have operational readiness tests where we go through a process that involves different subsystem teams working together. We have simulated the closest approach sequence on the spacecraft to make sure it does what we expect. –Cathy

Tell us something we don’t know about NASA. Do you get free stuff? Are there meetings where you learn cool things all the time? How many aliens have you guys captured and do they all live in Idaho?

NASA receives less than 1% of the federal budget each year.
Everyone gets free stuff: we post all of the data from our spacecraft to the web for everyone to see.
I have never been to a meeting where I did not learn something new!
There are zero non-terrestrial residents in Idaho. (source: US Census Bureau)

When will new LORRI images be released?

This is Michael Vincent: Keep your eyes on the New Horizons website: There should be a new image posted shortly.

When will New Horizons cross the heliosphere, and will the probe still be alive by then?

This is Michael Vincent: Because the location of the heliopause “breathes” with the activity of the sun and moves by many AU, so the exact date is impossible to determine. It won’t be until the late 2030s at the earliest.

What do you think Pluto will look like? And what is Pluto made out of?

There will be strong contrast on the surface, really dark and really bright, and other areas in between that will be red/brown colored. Inside, Pluto is mostly rock and water ice. On it’s surface it has ices made of nitrogen, methane, ethane, and carbon monoxide. There must be a lot of carbon rich stuff around as well.

How many other dwarf planets do you suspect are in our solar system that we haven’t detected yet? Are we talking about hundreds? Thousands?

This is Michael Vincent: In the Kuiper Belt, it is unlikely there are more than a few more that we haven’t already detected. Further out in the Ort cloud, however, there could be many more (could be hundreds or thousands).

Will new horizons get out further than voyager?

Nope. New Horizons was the fastest spacecraft ever launched, but Voyager had more gravity assists than New Horizons so it is now faster than New Horizons.

Is 1110113Y already confirmed as the follow-up target or is the team still weighing its options? How miffed are you at people referring to Charon as Pluto’s moon?

We’re still evaluating between possible KBO targets. About Charon, it’s Pluto’s biggest moon, no problem there. It’s also a planet in it’s own right by my standards, just like the big moons of some closer planets. Sometimes things fit into multiple categories, even on Earth you can be both a city and a state. Just ask Google!. -Alan

Compared to bodies farther than Pluto, what makes Pluto so special?

It’s the whole package! Many moons, surface activity, complex and changing atmosphere, clear surface markings, none of the others we know have all those in one system!

I’m a soon-to-be Computer Science graduate with a longstanding interest in all things space. What’s the best way to get a career in space development? Should I pursue the academic route of BSc + MSci + PhD, or is there another way? What are some fields of Computer Science that are relevant to space? I’m very interested in sensor fusion and machine learning.

This is Michael Vincent: The best way is to start looking around for internships while you are still in school. As far as degrees, it takes all types. Pick something you like and are good at, then keep looking for openings.

This is Kelsi: You could look for internships with a big lab like the Jet Propulsion Lab or the Applied Physics Lab – you can contact people there and ask if there is any internships/work that you could do there as a student or new graduate – or look for a place local to you where any space-related science is done and ask there! There are tons of ways that computer science graduates can be of use to space programs, so don’t be shy asking :).

How did you decide on the final shape, instrumentations and the name of New Horizons?

Alan here. Shape was decided by many design aspects and requirements, but loosely based on the Ulysses probe to Jupiter which also had just 1 RTG, unlike Voyager’s 2 RTGs. The instruments were chosen to answer NASA’s request for certain data sets and scientific objectives and to be most competitive against other proposals. I chose the name to symbolize the exploration as aspect of the mission.

How is the spacecraft doing on fuel? How much DeltaV is left approx.?

Michael Vincent: We are doing great on fuel. After Pluto encounter, and all the downlink, we will still have ~130 m/s left in DeltaV.

What would be the most surprising thing for the team to learn from the data collected on this mission?

Alan here, there is SO LITTLE we know, its hard to guess what would be most surprising. I guess most surprising would be to find there are no surprises.

How has the discovery of additional moons affected the Mission thus far, at what distance from Pluto would you be able to detect as of yet undiscovered moons (preferably expressed in time rather than distance) and would that allow for any additional changes to the plan?

We should start to be sensitive to seeing additional moons in June.

I understand that the spacecraft getting hit by (micro-)meteoroids during the encounter was a concern earlier in this mission. How big is the risk considered to be now? What countermeasures, if any, is the team taking?

Our best estimate of the risk of a dangerous impact is now less than 1%. The New Horizons team has done a lot of work in the last two years to understand the risk better, including more sophisticated models of how dust would move in the system. It is always prudent to be prepared: New Horizons is taking pictures when we get close to search for dust, and our team has prepared and tested an alternate set of observations that turns the antenna toward the direction we’re moving for a few hours.

I’ve always been curious, what would it take for a spacecraft to be able to orbit Pluto? Could you give us some really rough ballpark figures with regards to the fuel/time/cost requirements for a hypothetical Pluto orbiting mission? Would it be at all feasible with today’s technology, or would the weight and other constraints make it totally unfeasible?

To get to the Pluto system in only 9 and a half years, we sent a small spacecraft on a large rocket. New Horizons is traveling at about 14 km per second. New Horizons launched on a huge Atlas V rocket to get to that speed. To slow down, we’d need the fuel of another Atlas V! But to carry that, we’d need more fuel, and then more fuel to carry that fuel. — Leslie

What power level/flux do we receive on earth from NH transmissions? What power does the spacecraft receive from Earth transmissions?

Michael Vincent: So am I! Our typical received power at Pluto is around -120 dBm. Our receiver is so sensitive it would lock to something as low as -160 dBm.

It’s been a long time since launch, you’ve probably had time to plan out everything. What’s still uncertain with respect to the encounter (besides what Pluto will be like)?

One of the main uncertainties we’re working with is planning the final details of DSN (Deep Space Network) planning.

How long will New Horizons continue observing Pluto & Charon after the flyby – will you continue until September whilst you still have better than Hubble resolution or do you have to stop sooner because New Horizons can’t look too close to the Sun?

We have intensive imaging of Pluto and Charon planned through July. After that, we haven’t decided. As we are flying away from Pluto, the Sun is ~15 degrees away from Pluto as seen from New Horizons and we can take images of Pluto with the Sun that far away. — Cathy

Can you describe the details of the radio science experiment you will do during the Pluto flyby?

This is Michael Vincent. I have been lucky enough to work on the RF and REX instrument for the last 10 years! In broad strokes, the DSN sends up a 20 kW X-band signal that is very very stable in frequency and amplitude. Onboard, we have an ultra-stable oscillator that the RF system uses to down-convert the signal and send it over to the REX instrument. REX has a digital filter (also referenced to the oscillator) that splits the signal up into in-phase and quadrature components, and then records it on the Spacecraft. By analyzing that signal, our scientists can look for any faint wobbles in amplitude and phase, and determine the nature of the atmosphere the signal had to travel through.

How much speed are you guys planning to bleed off on the approach? Has most/all of the braking already occurred?

This is Michael Vincent: We aren’t really braking on approach. It is more important to fly through the system at exactly the right point, so that all our pre-planned observations are looking in the right place to find Pluto and its moons.

When is New Horizons expected to go offline, i.e. having used all of its available energy sources completely?

This is Michael Vincent: The prime mission will be over when all the data is to the ground, somewhere around the end of 2016. The RTG power supply will be able to keep critical systems powered until the late 2030s.

Is there talk of using New Horizons to attempt locating any hidden objects (the extra wobble on the sun) that are exerting gravitational influence?

This is Michael Vincent: New Horizons is a Pluto and Kuiper Belt mission, so if we are approved for an extended mission, we will target another KBO (Kuiper Belt Object) and head thataway.

Will New Horizon’s trajectory take it out of the solar system like Voyager 1 and 2? If so, will it be headed to specific area? Does it also contain an encoded greeting to other civilizations?

Yes, it is heading out and out. It does not contain a greeting to other civilizations, but it does contain a CD filled with names of people who wanted to send their names to Pluto.

Have you already planned the parameters for your trajectory correction manoeuvre? How much would you miss Pluto without it?

We have an opportunity for a trajectory correction maneuver (TCM) March 10. We are still refining our plans but may have a TCM that would be about a 1 m/s burn. Without this TCM we could be off by ~10,000 km.

How fast will the probe be moving relative to Pluto at its closest approach? How much detail will be get on Pluto and its moons?

We’re moving about 14 km/sec at Pluto, do the math for km/hr or day! We will image Pluto and its biggest moon Charon best, with the very best images having better than 100 meter resolution. For reference, that’s MUCH better than many first exploration missions, we’re proud of that!

From what I found Pluto has a rotation period of just over 6 days. Will NH have time to image the whole surface?

Pluto’s rotation period is ~6.4 days and we will have time to image the whole surface multiple times over.

How many other moons in stable orbits could there be around Pluto?

There could be lots, particularly far from Pluto. In close, the system is gravitationally jammed packed, so we expect at most only a few. But then again, this is first time exploration, so we could be really surprised!

Ever since the discovery of Pluto, what have we (as in, the scientists) learnt so far from it?

Since Pluto’s discovery in 1930, we have learned many different things about Pluto including it has 5 moons (that we know of today), a thin atmosphere (about one million times less dense than earth), Pluto has a surface with a lot of contrast (dark and bright patches), there are ices of nitrogen, methane, and carbon monoxide on the surface.

What challenges do the low levels of sunlight out past Neptune present when photographing objects?

The sunlight at Pluto is about a thousand times fainter than it is at Earth. This is about as faint as dusk or dawn here. Just as that isn’t much of a challenge for your camera to adjust between noon and dusk, it was not much challenge for the New Horizons visible-wavelength imagers, LORRI and MVIC. For the New Horizons infrared camera, LEISA, and its ultraviolet camera, Alice, we planned our encounter to allow these observation to have long-enough exposure times to gather enough light from Pluto and its moons.

Other than visual inspection, what kind of science instruments is New Horizons equipped with, and what could it tell us?

New Horizons is flying two instruments that observe in visible wavelengths (LORRI and MVIC), and six other instruments besides. The Alice ultraviolet spectrograph will mainly study Pluto’s atmosphere. The REX radio experiment will also study Pluto’s atmosphere and measure the temperature of its surface. The LEISA infrared imaging spectrograph will mainly study the composition of the surfaces of Pluto and its moons. The two plasma instruments, SWAP and PEPSSI, will measure Pluto’s escaping atmosphere and its effect on the solar wind. Finally, the Student Dust Counter will measure the dust environment of the outer solar system. — Leslie

What sort of ISO / how long are the exposures for an image of the planet?

Observations with LORRI, our high resolution camera, have typical exposure times of 0.1 sec. Our color observations, with the Ralph instrument, have expoHow big is the sun seen from New Horizons?sure times of ~0.6 seconds. — Cathy

How big is the sun seen from New Horizons?

Michael Vincent: 1-arcmin (or 1/60th of 1 degree).

What is it that you guys are looking for exactly on Pluto?

Our mission objectives are really about exploration– no mission has even been to a Kuiper Belt planet before. So we will be going with eyes wide open to map Pluto and its satellites, map their surface compositions and temperatures, assay the composition and temperature/pressure structure of Pluto’s atmosphere, look for new satellites and rings, and to search for an atmosphere around Charon too.There’s more, but that’s the basics…

How close will NH come to pluto? Is that distance the optimal ‘zone’ for the camera to get the best shots? If not then why can’t NH go closer?

New Horizons will fly 12,500 km from Pluto’s surface. This is the optimal zone balancing several science goals. The cameras like to see Pluto at intermediate phase angles — “looking at it sideway” — and so the distance balances being close to Pluto and having enough time to take pictures at these interesting phase angles.

Will New Horizons leave our Solar System? Will it be able to send any data or images after it passes Pluto and the other small KBOs you want to explore?

Yes, we’re on an escape trajectory from the solar system already. We expect to complete the data download from Pluto by late 2016 (we take data about 1-0-x faster than we can send it back). If we fly an expended mission after Pluto we could be sending new still data for years!

How long has this been in the works?

This is Marc Buie here. New Horizons launched in 2006 so the journey across the solar system has taken 9 years. Sounds like a long time but for me, my journey began in 1982 when I began studying Pluto, helping to learn more and building a case for the flyby this year.

What is the next mission that you really hope gets funded (regardless of the likelihood)?

You knew this was coming– our extended mission!