Estimate upper atmosphere density by combining onboard accelerometer measurements with orbital decay and attitude data. Produce a dataset showing density variation across sunlight and eclipse and compare to public models.
Estimate upper atmosphere density by combining onboard accelerometer measurements with orbital decay and attitude data. Produce a dataset showing density variation across sunlight and eclipse and compare to public models.
This is a intermediate-level project with an estimated timeline of 14-20 months using a 0.5U form factor.
The density of the upper atmosphere determines how quickly satellites lose altitude to drag, directly affecting mission lifetime, reentry predictions, and collision avoidance calculations. Despite its importance, atmospheric density above 200 kilometers is poorly measured it varies dramatically with solar activity, geomagnetic storms, time of day, and season, and the models used to predict it can be off by thirty percent or more. A density measurement payload uses the satellite itself as a probe: by precisely tracking how the orbit decays over time and combining that with knowledge of the satellite's shape and mass, the average atmospheric density along the orbital path can be inferred. An onboard accelerometer provides a direct but noisy measurement of drag deceleration, while GPS position and velocity data enable ground-based orbit determination for a more precise but less time-resolved density estimate. The experiment compares both approaches against widely used atmospheric models, quantifying model accuracy under different solar and geomagnetic conditions. The scientific contribution grows with mission duration every additional month of data improves the statistical significance of the density climatology. This is best suited as a secondary experiment on a satellite that already carries a GPS receiver for its primary mission.
Onboard accelerometer (ADXL355, I2C, 25 µg/?Hz noise floor) + space-capable GPS receiver (piNAV-NG, ~$500-1,500) logging position/velocity at 1 Hz. Primary method: GPS-based orbit determination track semi-major axis decay rate over days/weeks, infer average drag, derive density using known ballistic coefficient. Secondary method: accelerometer direct measurement (limited by noise floor atmospheric drag at 400-500 km is 10?? to 10?? m/s², near or below ADXL355 sensitivity). Ground processing: compare derived density against NRLMSISE-00 or JB2008 atmospheric models. Log sunlit/eclipse flag for solar heating correlation.
Atmospheric drag acceleration at 300-500 km is 10?? to 10?? m/s² 3-4 orders of magnitude below COTS MEMS accelerometer noise floor (ADXL355: 25 µg/?Hz). Professional missions (CHAMP, GRACE) used multi-million-dollar ONERA SuperSTAR accelerometers. GPS-based approach (tracking orbital decay, inferring density on ground) validated by Spire CubeSats yields ~15-30% accuracy. Heavy computation is entirely ground-based onboard payload is essentially just a GPS receiver (may already exist on bus). Scientific contribution modest as standalone primary payload. Cost: $300-$800. Complexity: intermediate. Feasible as secondary experiment but not compelling as primary payload. Tier 3 note: fundamental physics barrier limits what COTS hardware can achieve.
This project spans 4 disciplines, making it suitable for interdisciplinary student teams.
Ready to take on this project? Here's a general roadmap that applies to most CubeSat missions:
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