CERES BDS Data Set Guide Abstract

This document provides a brief overview to the CERES BDS data set. For more detailed information about this product, see the CERES BDS Collection Guide (PDF).

The BiDirectional Scans (BDS) product contains 24 hours of instantaneous Level-1b CERES data for a single scanner instrument. The BDS contains instantaneous radiance measurements recorded every 0.01-second for views of space, internal calibration, solar calibration and Earth. It contains all elevation scan modes which include the normal Earth scan and the short Earth scan modes and both the fixed and rotating azimuth plane scan modes.

The BDS product includes:

Filtered broadband radiances for the total, shortwave, and window channels for each 0.01 second measurement
Geolocation and viewing geometry for every Earth-viewing measurement
Instrument status, engineering temperatures and voltages for each 6.6 second scan
Sun geometry, satellite position and velocity for each scan
All raw engineering and status data from the instrument

Additional information about the format and content of the BDS can be found in the CERES Data Products Catalog (PDF). Details concerning the science parameters and how they are calculated can be found in the CERES Algorithm Theoretical Basis Document for Subsystem 1.0 and in the BDS Collection Guide (PDF).

[A Portable Document Format (PDF) reader (such as Adobe Acrobat Reader) is required to open and view PDF documents.]

Summary of Changes:

The CERES Data Management Team and the Atmospheric Science Data Center (ASDC) at Langley use a Sampling Strategy, a Production Strategy and a Configuration Code (CCode) to track versions of CERES archival data products. In general, minor reprocessing changes are tracked by increasing the Configuration Code while major reprocessing changes result in a new Production Strategy. The Sampling Strategy identifies the satellite and instrument which acquired the data in the product.

A summary of changes made to the CERES BDS product is shown in the following table.

**Modification History of the CERES BDS Aqua Archival Product**
Sampling Strategy and Production Strategy	CCode	Available at ASDC	Impact on the BDS Product
Aqua-FM3_Edition1-CV³ Aqua-FM4_Edition1-CV³	033033	03/2006	An update was made to the scripts to select the correct ephemeris and attitude data files. Update to add Solar and Lunar Angles to the BDS. New SDSs: Solar Elevation Angles, Lunar Elevation Angles, Solar Azimuth Angles, Lunar Azimuth Angles. New fields in the Satellite-Celestial Vdata: Earth-Moon Distance, Solar Beta Angle, Solar Eta Angle, Lunar Beta Angle, Lunar Eta Angle, Lunar Longitude at record start, Lunar Colatitude at record start. Update to check when Solar Heating affects radiance counts, when this occurs the radiances are set to the CERES Fill-Value. Tighten Std. Dev. thresholds for the spaceclamp, to catch bit-flips that may occur in the data.
Aqua-FM3_Edition2³ Aqua-FM4_Edition2³	031033	11/2005	Update to read new SDSs and new fields in the Satellite-Celestial Vdata in Edition1-CV BDSs. Edition2 after 11/2005 will include these new SDSs and Vdata fields.
Aqua-FM3_Edition1³ Aqua-FM4_Edition1³	032031	08/2005	Updates to code to allow processing of Total and WN channel data in FM4 after the SW channel anomaly, which began on 03/30/2005. This update does not affect FM3 science data.
Aqua-FM3_Edition2³ Aqua-FM4_Edition2³	030032	04/2005	Updated to use same samples for spaceclamp determination as those used in Edition1. Update Solar Eclipse tolerance angle from 0.75 to 0.65 to avoid footprints being mistakenly flagged as being in a Solar Eclipse condition.
Aqua-FM3_Edition1³ Aqua-FM4_Edition1³	031030	03/2005	Radiance values set to fill-value when any channels raw data equal exactly zero. Update to check the 16-bit raw radiance value against the fill-value before moving to a 64-bit value for calculations. Update to properly handle the patch being uploaded for the WN Bridge Balance. Fix error causing a BAD spaceclamp flag being overwritten with GOOD and causing an erroneous spaceclamp to be calculated and used in radiance count conversion.
Aqua-FM3_Edition2³ Aqua-FM4_Edition2³	029030	09/2004	Update to set geolocation values to CERES fill-value when a bit-flip is encountered in the elevation counts.
Aqua-FM3_Edition1³ Aqua-FM4_Edition1³	030028	09/2004	Update to set geolocation values to CERES fill-value when a bit-flip is encountered in the elevation counts.
Aqua-FM3_Edition2³ Aqua-FM4_Edition2³	028029	06/2004	Update to fix Double Drift Correction initialization.
Aqua-FM3_Edition2³ Aqua-FM4_Edition2³	028028	05/2004	Update made to default spaceclamp region. Minor Changes expected in: CERES SW Filtered Radiance Upwards CERES WN Filtered Radiance Upwards CERES TOT Filtered Radiance Upwards
Aqua-FM3_Edition1³ Aqua-FM4_Edition1³	029027	05/2004	Update Double Drift Correction Algorithm. Changes expected in: CERES SW Filtered Radiance Upwards CERES WN Filtered Radiance Upwards CERES TOT Filtered Radiance Upwards
Aqua-FM3_Edition2³ Aqua-FM4_Edition2³	028027	03/2004	New SDSs containing double drift corrected counts added. New algorithm added to correct SW interference with the WN channel radiances. Double Drift correction added to radiance conversion to correct drift introduced by the Second Time Constant correction.
Aqua-FM3_Edition1³ Aqua-FM4_Edition1³	027025	03/2004	New SDSs containing double drift corrected counts added. New algorithm added to correct SW interference with the WN channel radiances. Double Drift correction added to radiance conversion to correct drift introduced by the Second Time Constant correction.
Aqua-FM3_Edition1³ Aqua-FM4_Edition1³	027027	09/2003	No Science Impact.
Aqua-FM3_Edition1³ Aqua-FM4_Edition1³	027026	08/2003	Corrected erroneous Second Time Constant equation.
Aqua-FM3_Edition1³ Aqua-FM4_Edition1³	026025	01/2003	Release of Aqua Edition1, updated ground to flight gains.
Validation version only available to CERES analysts. This version available to the CERES Science Team. This version available to the public.

**Modification History of the CERES BDS Terra Archival Product**
Sampling Strategy and Production Strategy	CCode	Available at ASDC	Impact on the BDS Product
Terra-FM1_Edition1-CV³ Terra-FM2_Edition1-CV³	033033	03/2006	An update was made to the scripts to select the correct ephemeris and attitude data files.
Terra-FM1_Edition1-CV³ Terra-FM2_Edition1-CV³	033032	01/2006	Update to add Solar and Lunar Angles to the BDS. New SDSs: Solar Elevation Angles, Lunar Elevation Angles, Solar Azimuth Angles, Lunar Azimuth Angles. New fields in the Satellite-Celestial Vdata: Earth-Moon Distance, Solar Beta Angle, Solar Eta Angle, Lunar Beta Angle, Lunar Eta Angle, Lunar Longitude at record start, Lunar Colatitude at record start. Update to check when Solar Heating affects radiance counts, when this occurs the radiances are set to the CERES Fill-Value. Tighten Std. Dev. thresholds for the spaceclamp, to catch bit-flips that may occur in the data.
Terra-FM1_Edition2³ Terra-FM2_Edition2³	031033	01/2006	Update to read new SDSs and new fields in the Satellite-Celestial Vdata in Edition1-CV BDSs. Edition2 after 11/2005 will include these new SDSs and Vdata fields.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	032031	08/2005	Updates do not affect the Terra science data. Updates to code to allow processing of Total and WN channel data in FM4 after the SW channel anomaly, which began on 03/30/2005.
Terra-FM1_Edition2³ Terra-FM2_Edition2³	030032	03/2005	Updated to use same samples for spaceclamp determination as those used in Edition1. Update Solar Eclipse tolerance angle from 0.75 to 0.65 to avoid footprints being mistakenly flagged as being in a Solar Eclipse condition.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	031030	03/2005	Radiance values set to fill-value when any channels raw data equal exactly zero. Update to check the 16-bit raw radiance value against the fill-value before moving to a 64-bit value for calculations. Update to properly handle the patch being uploaded for the WN Bridge Balance. Fix error causing a BAD spaceclamp flag being overwritten with GOOD and causing an erroneous spaceclamp to be calculated and used in radiance count conversion.
Terra-FM1_Edition2³ Terra-FM2_Edition2³	029030	09/2004	Update to set geolocation values to CERES fill-value when a bit-flip is encountered in the elevation counts.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	030028	09/2004	Update to set geolocation values to CERES fill-value when a bit-flip is encountered in the elevation counts.
Terra-FM1_Edition2³ Terra-FM2_Edition2³	028029	06/2004	Update to fix Double Drift Correction initialization.
Terra-FM1_Edition2³ Terra-FM2_Edition2³	028028	05/2004	Update made to default spaceclamp region. Minor Changes expected in: CERES SW Filtered Radiance Upwards CERES WN Filtered Radiance Upwards CERES TOT Filtered Radiance Upwards
Terra-FM1_Edition1³ Terra-FM2_Edition1³	029027	05/2004	Update Double Drift Correction Algorithm. Changes expected in: CERES SW Filtered Radiance Upwards CERES WN Filtered Radiance Upwards CERES TOT Filtered Radiance Upwards
Terra-FM1_Edition2³ Terra-FM2_Edition2³	028027	04/2004	New SDSs containing double drift corrected counts added. New algorithm added to correct SW interference with the WN channel radiances. Double Drift correction added to radiance conversion to correct drift introduced by the Second Time Constant correction.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	027025	03/2004	New SDSs containing double drift corrected counts added.
Terra-FM1_Edition2³ Terra-FM2_Edition2³	027027	09/2003	No Science Impact.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	026024	08/2003	Corrected erroneous Second Time Constant equation.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	025023	01/2003	No Science Impact.
Terra-FM1_Edition2³ Terra-FM2_Edition2³	026025	01/2003	No Science Impact.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	025022	12/2003	No Science Impact.
Terra-FM1_Edition2³ Terra-FM2_Edition2³	024023	09/2002	Release of Terra Edition2. Update to correct drift found in instrument gains over time.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	024021	07/2002	No Science Impact.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	022017	02/2002	No Science Impact.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	021016	09/2001	Add 3-channel intercomparison to check for bit hits. Provide the capability to process slow azimuth scan rate data. Correct error to properly identify Bridge Balance resets.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	018013	04/2001	Updated the scan profile tables to include the new profile with no internal calibration. The previous version did not properly handle this scan profile causing scan dependent offsets of 0.0 to be used instead of the correct values.
Terra-FM1_Edition1³ Terra-FM2_Edition1³	017012	11/2000	Updated Terra count conversion offsets to use the ground determined values since no deep-space calibration has yet been performed. Updated Edit Limits for Terra radiance conversion from wide open to values determined by examining the inflight data. QA flags are now written to BDS as sample level and scan level. Previous flags were written for each sample, even when flags were scan level values. Terra Second Time Constant coefficients were modified based on inflight data analysis.
Terra-FM1_Alpha Terra-FM2_Alpha	014010	04/2000 04/2000	Eliminated spaceclamp values with the moon in the field of view. Corrected extraneous data writes when processing multi-day Level 0 files. Potentially fewer records depending on processing conditions. Implemented instrument specific thresholds for the spaceclamp algorithm. Potential changes in spaceclamp values for some records. Added meaningful SDS dimension names as HDF attributes.
Validation version only available to CERES analysts. This version available to the CERES Science Team. This version available to the public.

**Modification History of the CERES BDS TRMM Archival Product**
Sampling Strategy and Production Strategy	CCode	Available at ASDC	Impact on the BDS Product
TRMM-PFM_Edition1-CV³ TRMM-PFM_Ed1-CV-TransOps³	033033	03/2006	Update to add Solar and Lunar Angles to the BDS. New SDSs: Solar Elevation Angles, Lunar Elevation Angles, Solar Azimuth Angles, Lunar Azimuth Angles. New fields in the Satellite-Celestial Vdata: Earth-Moon Distance, Solar Beta Angle, Solar Eta Angle, Lunar Beta Angle, Lunar Eta Angle, Lunar Longitude at record start, Lunar Colatitude at record start. Update to check when Solar Heating affects radiance counts, when this occurs the radiances are set to the CERES Fill-Value. Tighten Std. Dev. thresholds for the spaceclamp, to catch bit-flips that may occur in the data. New SDSs containing Double Drift corrected counts for all 3 channels added to the BDS. Double Drift Correction added to radiance count conversion to correct drift introduced by the Second Time Constant correction.
TRMM-PFM_Edition1³ TRMM-PFM_Transient-Ops2³ TRMM-PFM_FailingSensor³	021016	09/2001	Add 3-channel intercomparison to check for bit hits. Provide the capability to process slow azimuth scan rate data. Correct error to properly identify Bridge Balance resets.
TRMM-PFM_Edition1³	016011	08/2000	Crosstalk replacement set to ON for TRMM: radiance values set to fill-value when crosstalk is found. New SDSs added: Time-Ordered Analog Parameters, Drift Corrected Counts (per channel) The BDS is now written with HDF compression. Smaller file for user.
TRMM-PFM_Edition1³	015011	07/2000	Add check for crosstalk between detector channels. Fixed sign error in the Second Time Constant algorithm.
TRMM-PFM_Transient_Ops2³ TRMM-PFM_Edition1³	014010	11/1999 02/2000	Eliminated spaceclamp values with the moon in the field of view. Corrected extraneous data writes when processing multi-day Level 0 files. Potentially fewer records depending on processing conditions. Implemented instrument specific thresholds for the spaceclamp algorithm. Potential changes in spaceclamp values for some records. Added meaningful SDS dimension names as HDF attributes.
TRMM-PFM_Edition1³	011004	04/1999	Updated 2nd time constant and spaceclamp algorithms. Included valid radiances in the solar calibration product, BDSS. Updated Terra offsets and coefficients for FM1 and FM2.
TRMM-PFM_Edition1³	009001	10/1998	Changed Window channel width value to 3.7 from 3.6µm.
TRMM-PFM_Edition1³	008000	08/1998	Corrected along-track data flagging algorithm.
TRMM-PFM_Edition1³	007000	07/1998	No science impact.
TRMM-PFM_Edition1³	006000	07/1998	Changed TRMM offset files to include Deep Space Calibration offsets for each elevation position. Corrected Second Time Constant Algorithm. Changed geolocation from geocentric coordinates at top of atmosphere to geodetic coordinates at Earth surface. Added viewing angles in geocentric coordinates. Changed Window channel units to W/m²/sr/µm. Changed parameter names for geodetic coordinates.
TRMM-PFM_ValidationR1²	000019	02/1998	Corrected for Digital-to-Analog Converter updates during rapid thermal changes at sunrise/sunset. Used updated count conversion coefficients for each channel.
TRMM-PFM_AtLaunch¹	0016	12/1997	Began generating BDS.
Validation version only available to CERES analysts. This version available to the CERES Science Team. This version available to the public.

Examples of Data:

**Individual Radiances for a 6.6 second scan (660 samples) taken during cross-track scan mode**

Total Channel	Shortwave Channel	Window Channel

**An orbital swath of scans located on the Earth**

Cross-track Scan Mode	Rotating Azimuth Plane Scan Mode

References:

Blackadar, Alfred, "A Computer Almanac," Weatherwise, 37 (5), 257-260, October 1984.
Clouds and the Earth's Radiant Energy System (CERES) Data Management System Data Products Catalog (PDF document) Release 3, Version 2, March 2000.
Clouds and the Earth's Radiant Energy System (CERES) Algorithm Theoretical Basis Document, Instrument Geolocate and Calibrate Earth Radiances (Subsystem 1.0), Release 2.2, June 1997.
CERES Instrument Geolocate and Calibrate Earth Radiances Level 1 Instrument Science Data Validation and Consistency Plan, Release 1.1, March 1996.
CERES Instrument Geolocate and Calibrate Earth Radiances Architectural Draft Design Document, (Subsystem 1.0) Release 1.0, June 1996.
Currey, C., L. Smith, B. Neely, "Evaluation of Clouds and the Earth's Radiant Energy System (CERES) scanner pointing accuracy using a coastline detection system," Proc. of SPIE, Earth Observing Systems III, 3439, 367-376, 1998.
HDF User's Guide, Version 4.0, February 1996 (from NCSA).
Hoffman, Lawrence H., Willliam L. Weaver, and James F. Kibler, "Calculation and Accuracy of ERBE Scanner Measurement Locations," NASA TP-2670, 1987.
Jefferys, William H., "Julian Day Numbers".
Priestley et al., "Postlaunch Radiometric Validation of the Clouds and the Earth's Radiant Energy System (CERES) Proto-Flight Model on the Tropical Rainfall Measuring Mission (TRMM) Spacecraft through 1999", J. Appl. Meteor., 39 (12), 2249-2258, 2000.
Release B SCF Toolkit User's Guide for the ECS Project,June 1998.
Software Bulletin "CERES Metadata Requirements for LaTIS", Revision 1, January 7, 1998.
Smith, G. L., "Numberical Filtering of Spurious Transients in a Satellite Scanning Radiometer (Draft)", September 1997.
Smith, G. L., "Effects of time response on the point spread function of a scanning radiometer," Appl. Opt., 30, 7031-7037, 1994.
TRW DRL 64, 55067.300.008E; In-flight Measurement Analysis (Revision E), 18 March, 1997.
TRW DRL 87, D20889B; Instrument Operations Manual, (Revision B), 11 January 1996.

Contact Information:

Investigator(s) Name and Title:

Technical Contact:

Author/Data Center:

Acknowledgment: The requested form of acknowledgment for any publication in which these data are used is:

"These data were obtained from the NASA Langley Research Center Atmospheric Science Data Center."

The Langley Data Center requests a reprint of any published papers or reports or a brief description of other uses (e.g., posters, oral presentations, etc.) of data that we have distributed. This will help the Data Center determine the use of data distributed, which is helpful in optimizing product development. It also helps us to keep our product related references current. To assist the Langley Data Center in providing the best service to the scientific community, we request a notification if you transmit these data to other researchers.

Reference:The CERES Team has gone to considerable trouble to remove major errors and to verify the quality and accuracy of these data. Please provide a reference to the following paper when you publish scientific results with the CERES data:

Wielicki, B. A., B. R. Barkstrom, E. F. Harrison, R. B. Lee III, G. L. Smith, and J. E. Cooper, "Clouds and the Earth's Radiant Energy System (CERES): An Earth Observing System Experiment," Bull. Amer. Meteor. Soc., 77, 853-868, 1996.

Clouds and the Earth's Radiant Energy System (CERES) Bidirectional Scans (BDS) Data Set Abstract

Table of Contents:

Data Set Description: