Message-Id: Date: Tue, 20 Nov 2001 16:53:31 -0800 To: igsleo@igscb.jpl.nasa.gov From: Tony Mannucci Subject: [IGSLEO-29] GPS occultation data from CHAMP Sender: owner-igsleo Precedence: bulk ****************************************************************************** IGS LEO Mail 20 Nov 16:53:37 PST 2001 Message Number 29 ****************************************************************************** Author: Tony Mannucci and Tom Yunck We are pleased to announce the release of GPS occultation data from NASA's Blackjack receiver aboard the German CHAMP mission, which is managed by GFZ in Potsdam. These new data join NASA's SAC-C occultation data released earlier this year. Both data sets are available via anonymous ftp from JPL's GENESIS web site (http://genesis.jpl.nasa.gov). A first validation of the Champ GPS data has been carried out by GFZ and JPL. Preliminary results by both centers for precise orbit determination and atmospheric retrievals on CHAMP have appeared in the scientific literature. For each occultation event, raw phase observables are acquired at both GPS frequencies from two GPS satellites tracked through the rear-facing antenna: the occulting satellite and a higher elevation calibration satellite. Phase and pseudorange observables from all the GPS antennas are included in the files. Detailed information for data download is provided at the end of this notice. The GPS data, along with other CHAMP mission data, are also accessible via GFZ's CHAMP Information System and Data Center at http://isdc.gfz-potsdam.de/champ. Users of the CHAMP and SAC-C GPS data should be aware that this is still an area of intensive development at JPL. The BlackJack is an all new design attempting to make measurements in the lower troposphere never before accomplished. CHAMP and SAC-C are serving as vital developmental test beds for experimental GPS remote sensing techniques. We have previously announced the availability of raw data from the SAC-C Blackjack receiver. Please see: ftp://sideshow.jpl.nasa.gov/pub/genesis/level0/sac-c/Documents/announcement.010913 . As we gain knowledge and experience, we will continue to make changes to the flight software on both CHAMP and SAC-C. We hope many of you will be able to join in this process of discovery, and contribute to the many insights and advances that we can expect as these missions proceed. The CHAMP receiver is being managed by GFZ Potsdam, and changes to the GPS receiver acquisition modes may occur from time to time. A history of upgrades, operational modes, and software changes for CHAMP is available in the GENESIS ftp area at: ftp://sideshow.jpl.nasa.gov/pub/genesis/level0/champ/Documents/CHAMP_recvr.html. Similar information for the SAC-C receiver can be found at: ftp://sideshow.jpl.nasa.gov/pub/genesis/level0/sac-c/Documents/SACC_recvr.html . We ask that users who choose to download these data fill out the registration form appended to this email and send it to: leoops@sdsio.jpl.nasa.gov. Send inquiries to Gerald Manipon at leoops@sdsio.jpl.nasa.gov. The binary data are primarily intended for groups familiar with the technical details of occultation processing. Retrieved atmospheric profiles of refractivity, temperature, etc. generated at JPL will be made available in a few weeks from GENESIS. Similar quantities are also generated at the GFZ ISDC. Please contact that center for further details. High-rate ground data useful in processing these occultations are available from the International GPS Service (IGS) (See IGSLEO message number 9 at http://igscb.jpl.nasa.gov/mail/igsleo/igsleo.html). Precise orbit determination data from the CHAMP and SAC-C zenith-viewing antennas are available from GENESIS in RINEX format, Version 2.1, as are CHAMP and SAC-C precise orbit solutions computed at JPL for occultation processing (see below). The availability of these data is the result of outstanding effort from a number of individuals within the following groups and institutions: The CHAMP project managed by GFZ Potsdam - see http://op.gfz-potsdam.de/champ GENESIS group at JPL GPS Earth Observatory group at JPL GPS Systems group at JPL International GPS Service NASA Orbiter and Radiometric Systems group at JPL Raytheon Technical Services Company Satellite Geodesy and Geodynamics Systems group at JPL DATA DOWNLOAD INFORMATION ------------------------- Data are available via GENESIS at http://genesis.jpl.nasa.gov. The ftp link to Level 0 data becomes visible after clicking on "Atmosphere Data and Products". Anonymous ftp clients can be directed to the following address: ftp://sideshow.jpl.nasa.gov/pub/genesis/level0/champ/ Data are in subdirectories yYYYY/dDDD, where YYYY is the four-digit year and DDD is the three-digit day of year. GPS data are in files named, e.g CH-0-RDC-DMP-SC+NZ_2001_311_04_20_2_b.gpsM, where 2001_311_04_20 indicates the time of the dump: 2001_311 is the year and day of year (1-366) 04_20 is the hour and minute, and .gpsM indicates GPS raw data from the Main GPS receiver (.gpsR indicates the Redundant receiver). Occultation data are not present for all days. See the receiver operations file for more information. The data are stored in Blackjack format with a TRSR (Turborogue Space Receiver) wrapper, with a second wrapper added by GFZ. We provide a utility to remove the GFZ wrapper (champ_unwrap.c). We provide a reader, BJfmtl, which removes the TRSR wrapper and writes the data in ASCII format. The source code is provided in the following directory: ftp://sideshow.jpl.nasa.gov/pub/genesis/level0/champ/Software . Additional documentation is provided in the directory ftp://sideshow.jpl.nasa.gov/pub/genesis/level0/champ/Documents . README.011112 provides information on the data. CHAMP_recvr.html provides information on satellite and GPS receiver operations. README.satellite lists some satellite specifications. RINEX format files for the 10-second rate GPS data from the zenith-viewing antenna are available at: ftp://sideshow.jpl.nasa.gov/pub/genesis/rinex/champ . File names are, e.g. cham3120.01o.gz in subdirectory y2001/ for day of year 312 in 2001. Directory history is provided in: ftp://sideshow.jpl.nasa.gov/pub/genesis/rinex/champ/Documents . Orbit files in both earth-fixed and earth-centered inertial coordinates are provided in: ftp://sideshow.jpl.nasa.gov/pub/genesis/orbits/champ/quick . The orbits are described in: ftp://sideshow.jpl.nasa.gov/pub/genesis/orbits/champ/quick/Documents/README.quick. These are quick-look orbits which were used for processing the occultations. To obtain an orbit estimate for arbitrary times, we typically use Lagrange polynomial interpolation (polynomial of degree 10). A software utility for this purpose will be available shortly in the ftp area. Please submit a registration form (see below) or register on the GENESIS web site. If you have questions about downloading data, please contact leoops@sdsio.jpl.nasa.gov . General information on the CHAMP satellite is available from: http://op.gfz-potsdam.de/champ -- Tony Mannucci ,Task Manager, GPS Earth Observatory project and Tom Yunck, Manager, GPS Observatories Office Jet Propulsion Laboratory, California Institute of Technology Email: Tony.Mannucci@jpl.nasa.gov Tom.Yunck@jpl.nasa.gov Postal address (Mannucci): Jet Propulsion Laboratory, California Institute of Technology MS 138-308 4800 Oak Grove Drive Pasadena, CA 91109 Begin Registration Form ----------------------- Please complete this form and send to leoops@sdsio.jpl.nasa.gov using the following text in the subject heading: "New User Registration". Or, register your interest on the GENESIS site. Name: Affiliation: E-mail Address: Please select your area(s) of interest: ( ) Climate and Global Change ( ) Ionosphere and Space Weather ( ) Geodesy and Solid Earth Science ( ) Weather Prediction ( ) Precise Orbit Determination ( ) Other (enter in "Comments") Please indicate spacecraft of interest (check all that apply): ( ) CHAMP ( ) SAC-C Comments or Additional Information: End Registration Form --------------------- -- Tony Mannucci Supervisor, Ionospheric and Atmospheric Remote Sensing Group Mail-Stop 138-308B, Tel > (818) 354-1699 Jet Propulsion Laboratory, Fax > (818) 393-5115 California Institute of Technology, Email > Tony.Mannucci@jpl.nasa.gov 4800 Oak Grove Drive, http://genesis.jpl.nasa.gov Pasadena, CA 91109