Fly a precision timing payload that disciplines a local oscillator to GPS signals and measures holdover drift during GPS outages and eclipse transitions. Validate high-accuracy onboard timekeeping for future geolocation missions.
Fly a precision timing payload that disciplines a local oscillator to GPS signals and measures holdover drift during GPS outages and eclipse transitions. Validate high-accuracy onboard timekeeping for future geolocation missions.
This is an advanced-level project with an estimated timeline of 14-20 months using a 0.5U form factor.
Precise timekeeping is fundamental to navigation, communication synchronization, and geolocation. GPS provides excellent timing when available, but GPS signals can be blocked, jammed, or unavailable during certain orbital geometries. A GPS disciplined oscillator locks a local clock to GPS when signals are available, then maintains accurate time autonomously during outages a capability called holdover. The quality of holdover depends on the stability of the local oscillator, ranging from minutes of useful accuracy with a basic crystal to days with an atomic clock. This experiment flies a precision timing payload that characterizes holdover performance through naturally occurring GPS outages eclipses, attitude maneuvers, and orbital geometry producing a dataset showing how timing accuracy degrades over time under real space conditions. The results are relevant to both scientific applications (where correlated measurements across sensors require tight timing) and defense applications (where GPS-denied timing resilience is an active area of investment). The project teaches clock physics, control loops, RF reception, and statistical analysis, with complexity scaling from intermediate to advanced depending on the oscillator technology chosen.
Critical: standard COTS GPS receivers (u-blox) stop above 515 m/s (COCOM limits) LEO velocity is ~7.5 km/s. Need space-capable receiver: SkyFox Labs piNAV-NG (~$500-1,500) or NovAtel OEM615 (~$3,000-5,000). Tier 1 build ($1,000-2,000): piNAV-NG + SiTime TCXO + STM32 MCU implementing software PLL, achieving ~1 µs accuracy GPS-locked, degrading to 10-100 µs over hours holdover. Tier 2 build ($8,000-15,000): add Microchip SA.45s CSAC (~$5,000-10,000, 120 mW, 17 cc, 35 g, 20 krad tolerant) achieving ±1 µs holdover over 24+ hours. Log GPS availability, holdover drift through eclipse/sunlight cycles, radiation upset rates.
Israel SAMSON mission (Technion) demonstrated CubeSat GPSDO using AD9548 digital PLL + NovAtel OEM615 + OCXO on a single 1U PCB directly relevant precedent. Microchip SA.45s CSAC is 120 mW, 17 cc, 35 g, radiation tolerant to 20 krad. GPS-denied timing resilience is of significant DoD interest both scientific and defense-relevant value. PLL design requires control theory knowledge appropriate for junior-level ECE. Jackson Labs Technologies produces commercial CSAC-GPSDO modules for reference. Cost: $1,000-$15,000 depending on oscillator tier. Complexity: medium-to-high. Tier 2 recommendation high value if funded for CSAC.
This project spans 3 disciplines, making it suitable for interdisciplinary student teams.
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