本日のGPM 2014.05.02
引き続き順調に運用されているようです。
■GPM Update Fri, 2014-05-02 10:38 a.m. EDT [NASA]
The spacecraft performed two routine maneuvers. The first was a 180-degree yaw (left/right in the horizontal plane) turn. This is the second yaw turn that changes the orientation of the spacecraft; it is now flying forwards again. Yaw turns are performed approximately every 40 days for thermal control, as the angle between the spacecraft's orbit and the sun changes. This keeps the side of the spacecraft designed to remain cold from overheating.
The second routine maneuver performed was a delta-v burn to increase the velocity of the spacecraft and maintain altitude. An extremely thin layer of atmosphere still exists at GPM's altitude of 250 miles above Earth's surface. As the spacecraft flies through the thin gases, drag occurs, slowing – and lowering – the spacecraft. Delta-v burns occur weekly to maintain altitude.
以前の記事で太陽熱の関係で40日ごとに180度ヨー軸制御しているとありましたが、その2回目がちょうど本日行われたそうです。またGPM主衛星はISSとほぼ同じ高度約400kmの軌道を周回していますが、ISS同様に軌道維持のためデルタVを定期的に実施しているのだそうです。その頻度は毎週。
