Detecting Changes in UHF Relay Communications Data Volume Performance for Mars Surface Rovers

The Mars Science Laboratory (MSL) Telecom Operations Team and the Mars2020 (M20) Telecom Operations Team at the Jet Propulsion laboratory (JPL) are developing statistical methods for detecting anomalous data volume trends in UHF relay passes. The MSL and M20 projects rely on UHF relay for nearly all their scientific data and engineering telemetry. Although variations between predicted and actual UHF relay volumes are inevitable, it is essential to detect changes in UHF relay volume performance trends. Changes in volume performance may be indicative of Telecom hardware health issues, which was the case when the Mars Reconnaissance Orbiter (MRO) developed problems with one of its two Ultra-Stable Oscillators (USO), leading to intermittent loss of entire UHF relay passes and ultimately requiring the orbiter to switch to the second USO. Such changes can also be induced by terrain, and significant losses in average volume performance have a disruptive effect on mission planning and execution since the uplink planning process requires good estimates of upcoming data volume returns to plan science and engineering activities on Mars. The ability to detect changes in long-term volume trends not only enables UHF hardware health monitoring but also provides valuable information to the rover planning team during periods when terrain and multipath issues may impact volume return. We use multiple statistical tests, including Welch's t-test [1], the Kolmogorov-Smirnov test [2] [3], the chi-square test [4], and a test based on the Irwin-Hall [5] [6] distribution to detect changes in the cumulative distribution function of relay data volumes. Statistically significant changes, detected using an appropriate statistical significance threshold, are used to alert operations personnel to unusual trends in volume.