DATA_SET_DESCRIPTION |
Data Set Overview : This data set contains raw spectra from Near Infrared Spectrometer #1 on the LCROSS spacecraft. NSP1 was the primary instrument on LCROSS, and its boresight was the reference for all nadir-looking instruments. After the centaur impact, the LCROSS spacecraft kept the impact site within the field of view of this instrument until shortly before its own impact. Each file in this dataset contains a 100 pixel spectra in an ascii, single-column, tabular format. All spectra in this dataset used an integration time of 0.5 sec. The spectrometer's field of view was circular and 1 deg in diameter. The spectra in this dataset have targets named Moon, Earth and Calibration (i.e., not targeted). The time each spectra was captured is encoded in the spectra's filename like this: LCROSS_NSP1_RAW_.IMG where : YYYYMMDDHHMMSSmmm and YYYY : the four digit year; MM : the two digit month, DD : the two digit day, and so on through hours, minutes, seconds and milliseconds. The detached label for each spectra has the same filename as the spectra but with the 'LBL' extension. This dataset encompasses all raw spectra collected by NSP1 during the mission. Note that the archive's DATA directory is partitioned initially by payload data collection period. The data collection period called 20091009113022_IMPACT contains the data from one minute prior to the Centaur impact through the end of the mission. Other data collection periods periods contain data from various calibration targets. Related Data Sets : This dataset is closely related to the NSP1_PREHAD and NSP1_CAL datasets. This spectrometer transmits data through the spacecraft to the ground in a format that is processed to create these raw spectra. The processing algorithm is a kind of Fourier transform called a Hadamard transform. The pre-Hadamard data for this spectrometer is contained in a dataset described in NSP1_PREHAD_DS.CAT in this directory. This algorithm is deterministic and has no inputs other than the pre-hadamard data, so reprocessing that data to generate updated raw spectra is unlikely. However, the pre-hadamard data is used to determine whether spectra contain saturated pixels. This dataset is not as closely related to NSP2_RAW and NSP2_CAL. Unlike the camera pairs which had overlapping fields of view, NSP1 and NSP2 were pointed in different directions. NSP1 was pointed downward, toward the centaur impact, while NSP2 was pointed toward the sun to measure absorption spectra. Parameters : Science ------- No instrument parameters vary within this dataset. The integration time is uniformly 0.5 seconds. Housekeeping ------------ Instrument temperature at the data collection time is reported in the label file under INSTRUMENT_TEMPERATURE and INSTRUMENT_TEMPERATURE_COUNT in degrees Centigrade and raw counts, respectively. This is a single telemetry point most representative of the instrument chassis temperature. Processing : Each near-infrared spectra was digitally transmitted from the spectrometer to the spacecraft in its pre-hadamard transformed format, inserted into a packet uncompressed and downlinked in telemetry. On the ground, the spectra were extracted from telemetry, the hadamard transform was applied, and they were converted to CSV format. The LCROSS Make Archive program read these files and wrote them as PDS-formatted table (.TAB) and label (.LBL) files. Data : The files in this dataset are PDS-formatted, ascii, single-column tables with detached label files. Coordinate System : The label files for these spectra contain the spectrometer's boresight vector in J2000 Geocentric Inertial frame. Software : The GSEOS Version used to generate these spectra is GSEOS 5.2.407 (Feb 25, 2008), Python 2.2.3 (#37, Nov 28, 2003, 04:20:20), Project Version 6.1.064. The LCROSS.py Python script used with GSEOS is Version Jun 11, 2008. The LCROSS Report Generator used on GSEOS created CCSDS.dat files is version 114. The version of Satellite Toolkit used to prepare geometric information for the labels is 8.1.3. The LCROSS Make Archive program used to assemble the PDS-formatted submission is dated 03/14/2010.
|