Tom Flatley, computer engineer and current head of the Science Data Processing Branch at Goddard Space Flight Center, leads a group of engineers and programmers in their development of flight and ground-based science data processing systems and applications, including SpaceCube, CubeSats/SmallSats, modeling/simulation/visualization, and other technologies.
NASA Tech Briefs: Why will NASA require improvements in on-board computing power?
Tom Flatley: Many of the next-generation instruments currently being developed are going to produce tremendous data volumes, and at extremely high data rates. Their needs are surpassing the capabilities of current flight processing systems, so what we’re trying to do is enable an order of magnitude or more improvement in on-board processing power so that we can handle the large data volumes and high data rates that the next generation of missions will require.
NTB: What is SpaceCube?
Flatley: SpaceCube is a hybrid science data processing platform that we’re developing. When I say hybrid, I mean it’s composed of traditional CPU resources plus field programmable gate array (FPGA) and digital signal processing (DSP) resources. We develop applications that use the benefits of each of these processing technologies to accelerate the execution of science data processing algorithms.
By using the new radiation-tolerant, but not radiation-hardened, hybrid processors, we can take advantage of the speed that the commercial devices can achieve, which is an order of magnitude higher than the traditional flight processors. Then we just develop strategies to detect and correct when they’re upset by radiation in space, basically fix it, accepting that we may have had a “blip” in the data, and keep going with the processing.
NTB: Can you explain a bit more about upset mitigation and how SpaceCube enables that?
Flatley: Traditional flight processors are, by design, radiation-hardened. When the chips are developed, they specifically build them using technologies that are immune to being upset in the space radiation environment. Radiation-tolerant devices are designed so that they won’t have destructive failures in space, but they can have what you can think of as “bit flips,” where a 1 changes to a 0 or a 0 changes to a 1. A “bit flip” can produce incorrect data temporarily, but you can detect that and fix it, or you can continue your processing, and the error will wash out and your correct processing will continue. The traditional devices, which are designed specifically such that they cannot be upset, are typically larger and slower, and they cannot perform at the rate that the current commercial ground-based processors can. So what we’re trying to do is find a middle ground where we can take advantage of the ground-type capabilities for high-end processing, and make them operate reliably enough in space that we can do science data processing applications.
We’re not trying to do man-rated health and safety. We’re not even trying to do critical spacecraft functions. For processing science data, typically it’s okay if you have a bad pixel every once in a while, or if you have to reset and start over again, as long as you’re providing 100x more capability that can provide the difference between being able to do your mission or not do your mission. Our strategy has been to use these high-end, radiation-tolerant devices, and then come up with techniques to detect and correct when they’re upset so that we can operate nearly as reliably as the radiation-hardened devices in space, for certain orbits and applications.
NTB: What do you mean by the “science data” that’s being processed? Is this image processing?
Flatley: It’s actually cross-cutting. We can support image processing, radar processing, or basically any kind of high-end processing needs. One good example: One of our scientists was proposing a radar instrument to go to Mars. With the current traditional processor, he could collect and process 9 minutes of data per day, and that filled up his on-board recorder. That was all that his processors could handle in a day. Using something like the SpaceCube, we did an R&D project with him where we moved some of his ground processing, which required more computing power than you could have onboard (but that is capable in the SpaceCube), and then just sent the pre-processed images down, rather than all the raw data. The first year we got a 6-to-1 data volume reduction, migrating the first set of his ground processing. The following year we got a 165-to-1 data volume reduction by processing the complete images onboard. Basically, he could run for 9 minutes a day using traditional processors, or he could run 24/7 using the SpaceCube and maybe have a bad pixel every once in a while. That’s the sort of enabling capability that we’re trying to deliver to the science community with the SpaceCube.
NTB: What other exciting capabilities do you see with SpaceCube?
Flatley: You can actually look at the data in real-time and react to events. For example, an earth science application meant to survey the Earth may detect a forest fire or a flood and could adapt its processing to change to an emergency-response mode, or send direct-broadcast, real-time pictures of the fire or flood down to the people in the field who are engaging it.
SpaceCube hybrid processing can enable autonomous robotic operations, like satellite servicing. In geo-orbit or lunar-planetary missions, you can have autonomous operations, and have enough intelligence there to operate without having a human in the loop all of the time.
NTB: Where is SpaceCube being used currently?
Flatley: It started out on the Hubble servicing mission 4. We flew our first Technology Demonstration in 2009, and that was our SpaceCube Version 1.0. Since then, we’ve come out with a version 1.5, a version 2.0, and a version we call “Mini,” which is a miniaturized version of the 2.0. We have several experiments on the ISS [International Space Station] right now that we’re doing in collaboration with the DoD Space Test Program. We’re also developing systems with the earth science folks here, and with the robotics servicing group, to do proof-of-concept work for their next-generation systems. We’re just now approaching the technology readiness level and the on-orbit demonstration level where SpaceCube can start being incorporated into real standard missions.
NTB: What kinds of experiments are being done on the Space Station?
Flatley: Our first experiment on the Space Station was just to run on some built-in data and demonstrate how we could detect and correct upsets in space. That’s been running on the Space Station since November of 2009, and we’ve detected hundreds of upsets. We’ve been able to correct all but six of them in real time, and not interrupt any operations. And the six times that we did have to reset, we were only down for a couple of minutes while we restarted. So we have a 99.9979% uptime, which demonstrates that the radiation-tolerant technology, for certain applications, can operate nearly as reliably as a fully radiation-hardened device.
Our new experiment, which was just installed this past September, is taking images of the Earth with high-definition Gigabit Ethernet cameras, and also controlling and reading data from a heliophysics instrument called “FireStation” that’s monitoring terrestrial gamma ray flashes from lightning storms, and that’s our first onboard demonstration of actual science data processing.
Our new experiment, which we’re working on now, will go on the Space Station in 2016. We’re going to be coupled with an earth-science sensor that’s going to measure methane concentrations in the atmosphere for greenhouse gas research, and also running an autonomous rendezvous and docking/ proximity operations experiment for the satellite servicing group.
NTB: What’s your specific work with SpaceCube?
Flatley: I’m the leader of the SpaceCube team, and we have a group of engineers and programmers here that work to develop the individual experiments, platforms and applications. I’m sort of the principal investigator, and then our team does all of the real development work.
NTB: You also do work with CubeSats and SmallSats. What will those do for spacecraft and spacecraft missions?
Flatley: A separate effort in our branch is working on CubeSat technology. We see, in the future, a need for two different classes of CubeSats. The first is the university-class CubeSats, which are being built right now. The second is a high-reliability CubeSat, and we’re working with the [Johns Hopkins University] Applied Physics Lab and several groups in the Department of Defense who want to build CubeSats that can do long-duration, 3-to-5-year missions, and maybe support the asteroid exploration or go to the Moon or Mars — basically as reliably as our regular satellites, but in a miniaturized package.
We have several efforts ongoing here at Goddard. There is a CubeSat and SmallSat Technology Working Group and a Tiger Team trying to come up with the key concepts and the architecture for this high-reliability CubeSat bus. For certain applications and certain proof-of-concept [projects], the university-class systems are fine. To really enable science in decreasing budget environments, a lot of our scientists now are looking to use smaller systems. We’re trying to make those systems more capable so that they can do higher-end functions or meet the reliability of our larger spacecraft. Typically, university CubeSats are getting better, but historically they have about a 50/50 chance of even working in orbit.
NTB: What are the technical challenges when trying to create CubeSats that work as reliably as regular satellites?
Flatley: Basically, it’s in the part selection and the design process. We’re working in sort of a “skunkworks” environment, implementing the same kind of design techniques and strategies that we do for our larger systems — just without some of the overhead of the formal process that we use with the larger satellites. Of course, the higher-reliability systems will cost a little bit more than the university-class systems, but they’ll also function a lot better. We’re trying to find a sweet spot in the middle, between keeping it simple but having it be reliable. We think we can really fill a niche with the NASA and DoD customers. We’re actually collaborating with people in DoD and the Applied Physics Lab because they have a common interest in this, to develop all the components that we need to make a modular, scalable, high-reliability CubeSat and SmallSat bus.
NTB: What do you think is the most exciting application for technologies like CubeSats and SmallSats?
Flatley: They’re getting better and better, and you can really do a lot with them, even things that it took a large satellite to do years ago. CubeSats are getting bigger. They started as a 1U, 10 x 10 x 10 cm spacecraft. Then, there was a 3U. Now there’s 6U, and people are working on 12U. When you get up to that size, you can really do a lot in a small space. Some of the instruments are getting smaller, and the technology across the board is advancing to the point where even a 3U or a 6U model can be as capable, or even more capable, than larger missions were 10 or 15 years ago.
I think it’s really going to be an enabling [technology] for both continuing to do science in a restricted budget, and enabling [applications] like quickly observing short-term phemonena or sending up fleets to get better spatial resolution on measurements. I think it’s really going to open up a whole new field to support the science community.
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