The Planck satellite in orbit mission ended in October 2013. Between the end of Low Frequency Instrument (LFI) routine mission operations and the satellite decommissioning, a dedicated test was also performed to measure the Planck telescope emissivity. The scope of the test was twofold: i) to provide, for the first time in flight, a direct measure of the telescope emissivity; and ii) to evaluate the possible degradation of the emissivity by comparing data taken in flight at the end of mission with those taken during the ground telescope characterization. The emissivity was determined by heating the Planck telescope and disentangling the system temperature excess measured by the LFI radiometers. Results show End of Life (EOL) performance in good agreement with the results from the ground optical tests and from in-flight indirect estimations measured during the Commissioning and Performance Verification (CPV) phase. Methods and results are presented and discussed.

中文翻译：

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普朗克望远镜发射率的飞行测量

普朗克卫星在轨任务于 2013 年 10 月结束。在低频仪器 (LFI) 常规任务操作结束和卫星退役之间，还进行了专门的测试以测量普朗克望远镜的发射率。测试的范围是双重的：i) 首次在飞行中提供望远镜发射率的直接测量值；ii) 通过比较任务结束时在飞行中获取的数据与在地面望远镜表征期间获取的数据来评估发射率可能下降的情况。发射率是通过加热普朗克望远镜并解开由 LFI 辐射计测量的系统温度过高来确定的。结果表明，寿命终止 (EOL) 性能与地面光学测试的结果以及在调试和性能验证 (CPV) 阶段测量的飞行中间接估计的结果非常吻合。提出并讨论了方法和结果。