Chen Yap, Planet Labs PBC; Mike Siegers, Planet Labs PBC; Andrea Maris Luis Valle, Planet Labs PBC; Ravi teja Nallapu, Planet Labs; Işil Demir, Planet Labs PBC; Kiruthika Devaraj, Planet Labs PBC; Scott McIntosh, Lynker Space
Keywords: Satellite Operations, Space Weather, NCAR Model, Differential Drag, Orbital Lifetime
Abstract:
Planet is a leading provider of global daily Earth observation imagery and geospatial analytics. Enabled in part by Planetscope Monitoring, the largest constellation of Earth Observation satellites (around 150 Doves), we drive towards our mission to make change visible, accessible and actionable. Planet’s Dove satellites operate within 400 – 550 km, which has been increasingly challenging as we approach the peak of the 25th Solar Cycle. Intense space weather around solar maxima increases atmospheric density throughout the Earth’s thermosphere (85 – 600 km); This effect is the most pronounced at LEO altitudes. Consequently the drag force that Doves experience within their operational altitudes increases dramatically as we approach solar maximum. In LEO constellations with limited maneuverability, mission lifetime is significantly shortened by heightened solar activity without accurate forecasting and the appropriate operational responses. Accurate forecasting of altitude decay is then of high importance in assessing and implementing operational responses. During 2023-2025, our LEO satellites orbit degraded at a faster rate than expected by predictions based on the Schatten model that is widely adopted as the industry standard by satellite operators. While the Schatten model has been a powerful tool in describing and forecasting solar flux in the 10.7 cm wavelength range (f10.7), recent Schatten predictions have not accurately reflected on-orbit flux values of the solar maximum. To ensure that we are accurately planning and assessing operational responses to the high flux, we adopted the Solar Cycle 25 model developed by the National Center for Atmospheric Research (NCAR). Instead of solely relying on solar magnetic cycles, the NCAR model also utilizes observations of previous sun-spot cycles to forecast f10.7 flux. In this work, we present both our operational responses to the solar maximum and utilization of the NCAR model to predict and evaluate the orbital lifetime utility of these responses. We also compare the forecasted improvements with actual improvements of each operational response. A critical improvement was achieved by experimenting with various differential drag configurations. The aim in our initial exploration was to minimize overall drag while preserving separation within the fleet. This separation is key to providing our customers with timely and useful imagery. Another avenue of improvement was incorporating extra mass in our build to increase the ballistic coefficient. We conclude that not only is the NCAR model a valuable tool in forecasting space weather and subsequent satellite orbital lifetime, it is also an effective tool in evaluating operational responses to high atmospheric density.
Date of Conference: September 17-20, 2024
Track: Atmospherics/Space Weather