The Processing Electronics and Detector of the Mars 2020 SHERLOC Instrument

摘要

The SHERLOC instrument (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) is an ultraviolet (UV) Raman and fluorescence spectrometer that will be deployed on the Mars 2020 rover mission. The instrument includes a context microscopic imager with resolution of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10\ \mu\mathrm{m}$</tex> , and the scanning laser has a spot size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$100\ \mu\mathrm{m}$</tex> , which allows SHERLOC to generate spatially and spectrally resolved data cubes without contact with the Martian surface (typically ∼5 cm of standoff from an abraded surface); it is designed to detect and characterize organics and astrobiologically relevant minerals in the search for past life. The instrument is led by Jet Propulsion Laboratory (JPL) with electronics, software, and electronic ground support equipment provided by Los Alamos National Laboratory (LANL), among others. The instrument is composed of two main physical components: the SHERLOC body assembly (SBA) and the turret assembly (STA). The SBA resides in the main body of the rover and operates in a relatively benign environment, while the STA is mounted on the rover arm turret and experiences extreme temperature fluctuations. The SBA conditions power from the rover, interfaces with the rover for command and data handling, and provides the control for the scanner and spectrometer. The SBA incorporates a LEON3 processor that runs all of the spectroscopy flight software. The STA houses the laser, laser power supply, imagers, scanning mirror, optics, and charge coupled device detector. The STA and SBA communicate via Spacewire over 12m of flex circuit routed down the rover robotic arm. The instrument is designed to autonomously scan a sample scene of approximately 7 × 7 mm, process the resulting data, and then subsequently interrogate regions of interest with much higher spatial and spectral resolution. This paper will describe the instrument spectroscopy electronics design and operation. It will cover the sampling and acquisition of data from the CCD, the detector noise performance, as well as storage and transmission of data to the vehicle.