Ott Melanie N, Thomes Joe, Onuma Eleanya, Switzer Robert, Chuska Richard, Blair Diana, Frese Erich, Matyseck Marc
NASA Goddard Space Flight Center, Greenbelt MD 20771.
AS&D, Inc., work performed for NASAGoddard Space Flight Center.
Proc SPIE Int Soc Opt Eng. 2016 Aug 28;9981. doi: 10.1117/12.2238561. Epub 2016 Sep 19.
The Advanced Topographic Laser Altimeter System (ATLAS) Instrument has been in integration and testing over the past 18 months in preparation for the Ice, Cloud and Land Elevation Satellite - 2 (ICESat-2) Mission, scheduled to launch in 2017. ICESat-2 is the follow on to ICESat which launched in 2003 and operated until 2009. ATLAS will measure the elevation of ice sheets, glaciers and sea ice or the "cryosphere" (as well as terrain) to provide data for assessing the earth's global climate changes. Where ICESat's instrument, the Geo-Science Laser Altimeter (GLAS) used a single beam measured with a 70 m spot on the ground and a distance between spots of 170 m, ATLAS will measure a spot size of 10 m with a spacing of 70 cm using six beams to measure terrain height changes as small as 4 mm.[1] The ATLAS pulsed transmission system consists of two lasers operating at 532 nm with transmitter optics for beam steering, a diffractive optical element that splits the signal into 6 separate beams, receivers for start pulse detection and a wavelength tracking system. The optical receiver telescope system consists of optics that focus all six beams into optical fibers that feed a filter system that transmits the signal via fiber assemblies to the detectors. Also included on the instrument is a system that calibrates the alignment of the transmitted pulses to the receiver optics for precise signal capture. The larger electro optical subsystems for transmission, calibration, and signal receive, stay aligned and transmitting sufficiently due to the optical fiber system that links them together. The robust design of the fiber optic system, consisting of a variety of multi fiber arrays and simplex assemblies with multiple fiber core sizes and types, will enable the system to maintain consistent critical alignments for the entire life of the mission. Some of the development approaches used to meet the challenging optical system requirements for ATLAS are discussed here.
先进地形激光高度计系统（ATLAS）仪器在过去18个月里一直在进行集成和测试，为计划于2017年发射的冰、云和陆地高程卫星-2（ICESat-2）任务做准备。ICESat-2是2003年发射并运行至2009年的ICESat的后续卫星。ATLAS将测量冰盖、冰川和海冰或“冰冻圈”（以及地形）的高程，以提供数据来评估地球的全球气候变化。ICESat的仪器——地球科学激光高度计（GLAS）使用单束光，在地面上的光斑尺寸为70米，光斑间距为170米，而ATLAS将使用六束光测量光斑尺寸为10米、间距为70厘米的地形高度变化，测量精度可达4毫米。[1]ATLAS脉冲传输系统由两台工作在532纳米的激光器组成，带有用于光束转向的发射光学器件、一个将信号分成6束独立光束的衍射光学元件、用于起始脉冲检测的接收器以及一个波长跟踪系统。光学接收望远镜系统由光学器件组成，这些光学器件将所有六束光聚焦到光纤中，光纤连接到一个滤波系统，该系统通过光纤组件将信号传输到探测器。仪器上还包括一个系统，用于校准发射脉冲与接收光学器件的对准，以实现精确的信号捕获。由于将它们连接在一起的光纤系统，用于传输、校准和信号接收的较大电光子系统能够保持对准并充分传输。由各种多光纤阵列和具有多种光纤芯尺寸和类型的单工组件组成的光纤系统的坚固设计，将使该系统在整个任务寿命期内保持一致的关键对准。本文讨论了为满足ATLAS具有挑战性的光学系统要求而采用的一些开发方法。
