Hack-a-Sat 2020: After-Action Report

We’d like to report our story of participating  in this amazing event, organized by US Air Force Research Laboratory and DoD Defence Digital Service. It was our first CTF and most of our team members met each other a few days beforehand. We didn’t score very high, but had great fun nevertheless. Congrats to the  top 10 teams on the leaderboard – they will advance to finals of this competition:

More than 1300 teams participated and here is the total points distribution for all teams (you can see the difficulty curve!):

The event focus was definitely more on space and less so on cybersecurity. Most of the challenges required knowledge of technologies and subjects familiar to people in aerospace industry. Here is a list of selected challenges we found most interesting, in various categories :  

Astronomy, Astrophysics, Astrometry, Astrodynamics

  • Attitude adjustment” and “Space Book” – A number of boresight reference vectors collected by star tracker and catalog reference vectors are provided. Use this information to determine attitude quaternion in order to claim those challenges.
  • Digital filters, Meh”  – Using provided MatLab/Octave code, identify the bug in the attitude control algorithm and trip error condition to capture the flag. Requires understanding of quaternion operations and control theory.

Satellite Bus 

  • Magic Bus” – extract information from device memory, accessible through I2C bus (commonly used on cubesats). We can tantalizingly close to solving this challenge, but ran out of time.
  • Bytes Away!” – restore the communications with a satellite using NASA cFS (https://cfs.gsfc.nasa.gov ) and Ball Aerospace Cosmos (https://cosmosrb.com) software.

Ground Segment

  • Can you hear me now?” – Implement XTCE decoder for a telemetry stream from TCP socket. XTCE is a format for spacecraft data telemetry specified in XML and in use by NASA and ESA (https://www.omg.org/xtce/index.htm).
  • Talk to me, Goose” – using the design document of the satellite and Cosmos software, trigger the satellite into revealing  the flag. Previous challenge of creating XTCE decoder will come handy here.
  • “Vax the Sat” – login into a virtual VAX system and figure out what to do next 🙂

Communication Systems

  • Most of the challenges in this category revolved about decoding information from analog data, figuring out demodulation schemes, frequency spectrum and then finding out weaknesses in communication protocols. We came very close to solve one of these challenges, but got stuck at the final step. Minimodem (http://www.whence.com/minimodem/) and multimon-ng (https://github.com/EliasOenal/multimon-ng ) were very useful here.

Payload Modules

  • “That’s not on my calendar” ­­– another cFS/Cosmos challenge.
  • “SpaceDB” – rescue the satellite in distress using kubOS API (https://www.kubos.com).

Space and Things

  • “Where is the sat”  – requires knowledge of transformation between inertial reference frames, understanding of TLE data to predict location of the satellite for given time.
  • Good Plan? Great Plan! – Create a mission plan for satellite to take a picture of a specific location on the ground. Very much about space operations skills.
  • 1201 Alarm – A recreation of historical Apollo mission, using VirtualAGC simulator, putting you in the shoes of Buzz Aldrin and Neil Armstrong.

Organizers promised to make all challenges and solutions to be available for the public on the  https://www.hackasat.com website by June 19th. We are looking forward to that!

P.S. We (Exodus Orbitals) are also working on a project similar in spirit to Hack-a-Sat, a crowd-flyable cubesat. You can learn more about it (and subscribe to our mailing list) here:


History of CubeSats, Chapter Two: First Cubesats


Cubesats (or nanosatellites) represent an important chapter  in the history of New Space that may have been eclipsed by more glamorous stories of SpaceX, Rocket Lab or other players in launch industry. Nevertheless, emergence of simpler and cheaper satellite designs allowed smaller teams with smaller budgets to participate in space exploration. Notably, the first cubesats were launched a year before the flight of SpaceShipOne in October 2004, the first major event of New Space epoch.

First missions

Original cubesat specifications were published in year 2000 by Space System Development Lab of Stanford University. But the first real cubesats were launched on June 30, 2003 on a Rokot launch vehicle (a converted ICBM) as a secondary payloads, while MOST, a Canadian space telescope was one of the primary ones. They all were deployed into relatively high-altitude circular orbits with altitude over 800 kilometers and therefore still in orbit as of 2020. The missions and fates of all those satellites were very different and illustrative of both capabilities and limitations of the early cubesats. Let’s have a look at each of those missions in more details, starting with less fortunate ones:

  • CANX-1 was a 1U cubesat designed by University of Toronto, Canada. It was rather sophisticated for an early one, having an imaging camera, GPS receiver and proper attitude control and communication subsystems. Sadly, it never came alive after deployment and no signal was ever received from it. However it was not the last cubesat from University of Toronto Institute for Aerospace Studies and their later cubesat missions, starting with CANX-2, enjoyed more success. 
CANX-1 (Image credit: UTIAS-SFL, UoT)
  • The next in the list of less-than-fortunate ones was DTUSAT cubesat, another 1U one from Technical University of Denmark. Its primary mission was a deployment of electrodynamic tether and the secondary mission was Earth observation, meaning it had an imaging camera. It could be a pretty interesting mission, but again the satellite was dead after deployment, with no signal ever received from them. 
DTUSAT (Image credit: DTU)
  • The fate of AAUSAT-1, another Danish 1U cubesat from University of Aalborg was somewhat more fortunate. Its payload included an imaging camera as well. It became alive after launch and some radio signals were received from it. However, there were some problems with communications subsystem and those signals were very weak. Not much useful data were extracted on the ground. It was able to operate for two and a half months before its battery degraded. Still, it was a major step forward for cubesats in general.
AAU Sat (Image credit: AAU)
  • QuakeSat from already mentioned Stanford Space System Development Lab was  a mission to detect Extremely Low Frequency electromagnetic waves for potential earthquake prediction. It was a considerably larger cubesat, in 3U form-factor, that is 30x10x10 centimeters. Its mission was a lot more successful than of previously mentioned ones. The satellite operated for a year and half, producing valuable scientific results (short-duration ELF emissions were indeed detected, but reliable monitoring of these events requires funding beyond the scope of a single satellite mission). Here is another interesting fact about it: the RF transmitting power of this satellite was approximately 1 Watt, same as the transmitting power of the first satellite launched ever, Sputnik-1, back in 1957.
QuakeSat (Image credit: QuakeSat collaboration)
  • Next came two missions from Japanese universities. The first one to describe was named CUTE-1. It was designed by Tokyo Institute of Technology and its mission was testing transmission protocols for the space-to-ground communications. As with Quakesat before, this mission was also quite successful. It was fully operational at least until 2012, a very long time, considering the average cubesat lifetime is around two years. What is even more impressive is that CUTE-1 is still transmitting telemetry data, after almost 17 years of operations! 
CUTE-I (Image credit: TITech)

But another mission from Japanese team, 1U cubesat XI-IV has demonstrated even more impressive results. It was designed and built by University of Tokyo and had the primary mission of Earth Observation, meaning it had an imaging camera on board. And it was fully operational as late as June 2019, still able to produce the image with its CMOS camera and transmit it to the ground. Not bad for being also one of the first cubesats to reach orbit! Maybe we should learn a thing or two about satellite design from Japan.

XI-IV (Image credit: ISSL)

And here is the image gallery from XI-IV. You can see gradual deterioration of camera instrument, but the images are still legible enough to see Earth’ cloud cover.

Gallery of XI-IV images through 16 years of operations (The University of Tokyo)


  1. University of Toronto UTIAS-SFL Home Page
  2. Gunter’s Space Program Page
  3. Earth Observation Portal Directory
  4. On-orbit Operation Results of the World’s First CubeSat XI-IV – Lessons Learned from Its Successful 15-years Space Flight. Ryu Funase, Satoshi Ikari, Ryo Suzumoto, et al. University of Tokyo, 2019. SSC19-WKIII-09.

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History of CubeSats, Chapter One: What Is a CubeSat?

We begin a new series of blog posts by our team members, explaining some of the concepts behind our business model and technology.

Cubesats are a classification of small satellites that are measured in a volumetric called a U, This U is a cube of dimensions 10cm x 10cm x 10cm (hence the term cubesat) and a satellite can be built of a set number of U’s. Such as a 1U communications node, a 3U earth observation platform or a larger 12U space telescope.

To understand how the cubesat concept evolved we need to understand the traditional design philosophy of satellites that has only changed in the last decade. Back when the first satellite was launched in 1957 we were still in an era of analogue electronics where you would require a single vacuum tube the size of your fist to have a single transistor in your circuit, compared to the latest processors today that have billions of them over a surface area equal to your fingernail. This means that for early satellites to have any form of capability they would need to be large in size for even basic radio communications.

Over the past decade consumer electronics have become small, cheap and most importantly: reliable. This means you can get high capability in a small package, which is important when you consider that per kilogram it would cost you up to 35,000 US dollars to get anything into orbit. This led to the development of the small satellite classification where a system that can fit in your hand can be sent into orbit and can be a communications platform, a device that can track forest fires or even a development platform where new technology can be tested in space at a reduced cost. Such as our mission NOVA.

The big advantages that cubesats (and by definition small satellites) bring to the table is cost to market, for previous missions you would have to use space grade equipment which is traditionally high cost and size and following that chain would lead to a larger satellite that would require a dedicated launch, again leading to higher costs. In a smaller size using off the shelf components costs can be saved, and multiple cubesats can be carried in a single launcher under a rideshare programme which further reduces costs.

Due to the lower capability of cubesats compared to the larger projects led by the international space agencies they are used heavily in commercial applications, this means that they operate in low earth orbit (LEO) where the majority of earth observation and communication satellites are based, although LEO is classed as any attitude below 2000km this tends to be more in the 300km ballpark. Small satellites are seldom used in higher orbits such as geostationary orbit (GSO) due to the cost of a dedicated heavy launcher that can send larger payloads to such altitude in addition to these higher orbits being more restricted due to their unique properties.

Mark Perkins

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