The 1A-AUX and CPR level 0 data products are combined to produce the Level 1B-CPR product. (Note: They are not provided as Standard Data Products, however are described here because these two products are combined, with little additional processing (calibration and addition of metadata), to form the Level 1B product.)
(The following is an excerpt from the 1A-AUX Description and Interface Control Document. The entire document can be viewed from the CloudSat Standard Data Product Interface Control Document links page.)
CloudSat Science and Engineering Data will be down-linked, from the CloudSat on-board data recorder, through the Air Force Satellite Communications Network (AFSCN) to the USAF RDT&E Support Center (RSC) in Albuquerque NM. There the data will be decommutated, checked for transmission errors (checksum), and stored on-line as a set of binary files. These raw data will be accessed by the DPC, via internet/ftp, for subsequent level 0 through level 2 processing.
As it arrives, Raw CloudSat science and auxiliary data will be pre-processed to form a time-ordered data file (with duplicate data packets removed and missing data blank-filled/flagged). These data are then further processed and stored on the local DPC mass storage system by orbit (plus approximately 10 minute overlaps on the front and back of each orbit – required by level 2 processes).
A 1A-AUX file will be created for each CPR Level 0 data file. The 1A-AUX file will match the CPR level 0A file record by record, with each data record linked by time.
The processing will proceed as follows: The CPR profile sample time will be extracted from the CPR Level 0 data file and used to index into the EU-SSOH data file and Definitive Ephemeris file to extract data that is necessary to build the 1A-AUX file. The 1A-AUX file will then be written out, by granule (orbit) for later ingest by the Level 1B processor.
The data products that are required for the production of the 1A-AUX file (each of these will be described in more detail in the following sections of this document) are:
CPR Science Data
The CPR data will be received approximately 8 times per day. These data "dumps" will contain overlapping orbits, or partial-orbits, with each data "profile" (a CPR radar, vertical sample) identified with a unique time stamp. These data will be pre-processed to remove duplicate data packets and to produce a quick-look display of the raw CPR counts for each of the 125 vertical "bins" in each profile.
This "raw" (level 0A) CPR data stream will be parsed to locate the VTCW (epoch time from the spacecraft), second counter, and millisecond counter fields which will be used to match these data with the other auxiliary data products required for the production of the 1A-AUX file.
EU-converted, State of Health (EU-SOH) and Stored State of Health data (EU-SSOH)
The EU-SSOH data will be stored in text files as comma-delimited fields. These data will normally be ingest at the same time as the level 0 CPR Science data, but may be received as late as six hours after the receipt of the corresponding CPR data.
The Stored State of Health (SSOH) files will be processed to remove duplicate packets of data, and data will be extracted, indexed to each CPR profile, and written out to the 1A-AUX file.
In the event that SSOH data is unavailable, SOH data may be used to replace the SSOH data. The SOH data is formatted in the same way as the SSOH data.
Definitive Ephemeris
The Definitive Ephemeris data will be received once per day at approximately noon Mountain time. This file will contain time, satellite position, and geo-location fields (lat/lon and height of spacecraft) at 1-second intervals.
The time information from the CPR science data will be used to index into this file and parse out the geo-location data for each CPR profile.