What I Learned Today

I recently joined the Mars Exploration Rover team as a TAP/SIE (Tactical Activity Planner / Sequence Integration Engineer) for the Opportunity rover. That means it’s my job to sit in on the morning SOWG (Science Operations Working Group) meeting, in which the rover’s scientific goals for the day are set, and then work with payload, thermal, downlink, mobility, and other experts to come up with a plan to achieve those goals. What pictures will we take? When? Where will we drive? Is there enough power?

Reading the training documents only gets you so far. I’ve just begun “shadowing” the current TAP/SIEs so that I can learn on the job, watching over their shoulders through a day of planning. My first shift was on Wednesday, and it was supposed to be an “easy” day: pick one of two rock targets, drive towards it, and take some pictures looking backward at yesterday’s tracks.

Scientists dialed in from all over the country for the SOWG meeting. After some debate and consultation with the Rover Planners, they settled on the rock that had the easiest approach. The scientists signed off and we went to work building the plan.

The TAP/SIE’s job is facilitated by a bewildering array of scripts and tools. These allow for the setup, development, refinement, and checking of the plan. Are power or thermal constraints violated? Do we have enough onboard storage space for the new images to be collected and enough downlink allocation to get them back to Earth?

While the RPs (Rover Planners) settled in to their job of constructing the drive sequence, we worked on the full sol’s plan (a day on Mars, which is 24 hours and 40 minutes in Earth time, is called a sol). Very quickly we realized that the planned drive, despite covering only a couple of meters, would drain the rover’s battery dangerously low. Opportunity was starting the sol at only 80% charge because of two long instrument observations the previous sol.

We modified the plan to give the rover a morning “nap” in which it could sun itself and collect power, like a desert lizard. That helped the power situation, but not enough. Several iterations later, we finally squeaked by at 0.1 Amp-hour above the required threshold.

Meanwhile, the RPs were growing concerned about a different problem. To reach its goal, Opportunity would have to straddle a rock that, while small by human standards, could pose a risk to the rover’s instrument arm, which dangles slightly down when stowed for driving. The RPs put their 3D simulation of the rover and the terrain up for all to see, and we stared at the screen while they spun the rover and tried to examine the rock from all angles.

“Can we raise the arm while it drives over the rock?” I whispered to the TAP/SIE I was shadowing. “It’s risky to do that,” she whispered back. “The arm bobs around, especially going over a big rock.”

A few minutes later, a scientist on the telecon asked, “Can’t we just put the arm up?” but was quickly shot down by the TUL (Tactical Uplink Lead, head planner): “Too risky.” The TAP/SIE and I grinned at each other.

Ultimately, it was deemed too dangeous to drive over the rock with our current data (images the rover had taken the sol before), and they decided to drive up to that rock and stop. Post-drive imaging would illuminate the obstacle in more detail.

At the end of our shift, which apparently was two hours later than usual, we had a plan. We ran it through multiple checks and re-checks and manually confirmed all of the sequences. The final walk-through was punctuated with “check!” coming from different areas of the room as each person confirmed that their part was correctly represented. The plan was finalized and transmitted to the rover using the Deep Space Network later that night.

There’s nothing like seeing a job in action. I learned a lot about the steps involved in planning and (unexpectedly) a lot of re-planning. For the rover, today is “tosol” and yesterday is “yestersol.” I got to practice the phonetic alphabet, which is used to communicate letters (in rover sequence ids) with a minimal chance that they will be misheard. I even got to help out a bit as a second pair of eyes to catch typos, spot constraint violations, and suggest alternative solutions. And I’ll be back on shift next Monday!

Opportunity is near Endeavor Crater, working its way along a ridge that is at the perfect tilt to keep its solar arrays pointed toward the sun. This is important because Winter Is Coming, even on Mars, and we want to keep it sufficiently powered to make it through to spring — its fifth spring on Mars. (Opportunity landed 9.5 Earth years ago!)

Cybersecurity is a serious issue not just for computers on Earth, but also for those in space.

Last month, JAXA (Japan’s space agency) announced that hackers had broken in to gain access to information about the Kibo Space Station module. The information consisted of Kibo “operation preparations” and mailing lists. In September, a 16-year-old was sentenced to six months in jail for hacking into NASA (and other) computers. In early 2012, NASA’s Inspector General Paul Martin testified to Congress about the state of NASA’s cybersecurity defenses and woes. “In 2010 and 2011, NASA reported 5,408 computer security incidents that resulted in the installation of malicious software on or unauthorized access to its systems,” he said. This goes beyond hacking into an employee’s PC: “The March 2011 theft of an unencrypted NASA notebook computer resulted in the loss of the algorithms used to command and control the International Space Station.”

Naturally, the same concerns apply for our rovers on Mars.

On Tuesday, I attended a talk titled “MSL Cyber-security implementation status report” by Bryan Johnson and Glen Elliott of JPL. You can view the slides from a similar conference talk. They reported on the long list of actions the team has taken to increase the security of operations and commanding for the Mars Science Laboratory (MSL) rover. These include the implementation of Two-Factor Authentication for access to mission systems and applications, consolidating computers into a single virtual LAN, implementing and testing an “incident response process,” and taking obvious (but time-consuming and easy-to-overlook) steps like pruning the list of people with access to the MSL network.

These steps all aim to improve security here on the ground. I asked whether they would discuss measures being taken to prevent unauthorized access to the rover itself, such as encryption or authentication prior to the rover accepting commands. Unfortunately, they declined to discuss it, but the unofficial word is that there is little or no security on the rover side. Conceivably, anyone with a powerful enough antenna and the right pointing information could send the same kind of signals currently being transmitted by the Deep Space Network to all of our remote assets (rovers, orbiters, and other spacecraft). And as we know, security through obscurity only gets you so far. MSL has had a sufficiently high profile that a rumor began circulating last August that the hacker group Anonymous was trying to gain access to the rover:

MarsCuriosity: “Anyone in Madrid, Spain or Canbarra who can help isolate the huge control signal used for the Mars Odyssey / Curiosity system please? The cypher and hopping is a standard mode, just need base frequency and recordings/feed of the huge signal going out. (yes we can spoof it both directions!)”

A group dedicated to “Space Asset Protection” is looking into this side of the problem. Unfortunately, there is some reluctance to adopt encryption, which carries its own overhead in complexity and bandwidth consumption for the often severely limited data links available for spacecraft communication.

And as for authentication, there’s always the chance that the rover might suddenly say, “I’m sorry, Dave, I’m afraid I can’t do that.”

Jupiter’s moon Io is very active volcanically:

“A Giant plume from Io’s Tvashtar volcano composed of a sequence of five images taken by NASA’s New Horizons probe on March 1st 2007, over the course of eight minutes from 23:50 UT. The plume is 330 km high, though only its uppermost half is visible in this image, as its source lies over the moon’s limb on its far side.” (Robert Wright and Mary C. Bourke)

But what is that lava made of? What materials lie inside the moon that are being spewed out? We can’t (yet) land on Io and test its lava directly. But we can make some inferences based on remote sensing observations of the lava’s temperature. The temperature carries information about how mafic (magnesium and iron-rich) or felsic (silicon-rich) the lava may be.

The best way to test our ability to deduce composition from orbit is to do it here on Earth, where we do have the opportunity to determine the true composition by sampling the lava on the ground. Scientists Robert Wright, Lori Glaze, and Stephen M. Baloga recently reported a positive correlation between temperature observations from Earth orbit (using the Hyperion spectrometer) and ground composition observations of 13 volcanoes: “Constraints on determining the eruption style and composition of terrestrial lavas from space”. The conclusion for Io is that the lava is so hot that it is likely ultramafic: very high magnesium/iron content.

You can read more about this endeavor (and view more pictures).

The 1976 Viking landers conducted a handful of experiments that involved injecting a nutrient-laden solution into Martian soil, then measuring gases given off in response. Indeed, gases were observed from the regular soil, but not from soil that was first heated to 160 C (sterilized). That seemed intriguing to many scientists—but others noted that the same result could be obtained through (abiotic) chemical oxidation triggered by the application of water. If I understand the arguments, heating the soil would break down the presumed oxidizer in the soil so it would then react less or not at all to a new injection of moisture.

But lo and behold, the scientists who (still) insist that Viking found life have published a new paper: “Complexity Analysis of the Viking Labeled Release Experiments” by Bianciardi, Miller, Straat, and Levin. They’ve used “complexity variables” to characterize the time series data, then clustered them (with k-means clustering, k=2). Indeed, they found that presumed “active” samples (including some examples from Earth) clustered together while presumed “inactive” samples (including some controls from Earth) clustered in a different group.

Since my dissertation was on clustering, I thought I should take a look and see how this machine learning method was being used in this setting. And, well, I’m just not convinced. Yes, they do seem to have gotten two distinct populations. But they only used 15 samples (11 from Mars, 4 from Earth) and that hardly seems sufficient to characterize the range of behavior, nor are they all obviously comparable (one time series consists of “core temperature readings taken every minute from a rat in constant darkness”; how is this related to possible bacterial activity in soil? Is darkness relevant? What about a rat in daylight, or a diurnal cycle?). The authors have agreed that more data would be better. I think more data, and thoughtfully chosen, would be essential.

My other reservation is about the “complexity variables” that were used. These are presented with no justification or discussion:

• LZ complexity
• Hurst exponent
• Largest Lyapunov exponent
• Correlation dimension
• Entropy
• BDS statistic
• Correlation time

Especially since these generated the 7D space in which the clustering happened, it’d be nice to have some intuition about why these might relate to life. There are some brief comments about life being “ordered” and of “high complexity” (and I’ve worked on this subject myself!) but I’m not convinced that the distinction they found is truly meaningful.

I don’t want to be unscientifically biased or negative. The results as presented in the paper do seem to show a quantitative separation between active and inactive samples. But this should be conducted with hundreds or thousands of samples from the Earth at the very least, where we have tons of examples of life-bearing soils as well as artificial or sterilized samples. These could fill out the feature space and properly position the Viking observations in more context.

Of course, it would also be useful to get more Martian samples!

Most of what we know about Mars only goes skin deep. We’ve had several orbiters studying the planet with a variety of remote sensing instruments (cameras, lasers, radar, etc.) and several rovers running around on the surface. The Phoenix lander dug around in the soil a little.

But so far, we haven’t been able to look beneath that skin. No drills, no cores, no subsurface probes. We haven’t even gotten a seismometer to the planet, which could be used to learn about the composition of the planet’s interior, and help answer the question of whether Mars still has a molten core. (The Apollo astronauts put seismometers on the Moon to help answer similar questions.)

The InSight mission to Mars seeks to change that. InSight is a lander that will use a seismometer and a heat flow probe to learn about the planet’s interior. (It will also have a surface camera, of course!) The plan is for InSight to launch in early 2016 and land on Mars later that year.

We’ve studied Mars from the outside for decades now… it’s time to look under the hood!

InSight is competing with two other concepts to be the next Discovery mission to Mars. (The others are the Titan Mare Explorer and Comet Hopper.) One of the three will be selected in late 2012. Stay tuned!