92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Thursday, 26 January 2012: 2:30 PM
CERES Flight MODEL 5 On NPP: PRE-Launch PERFORMANCE and SDR Validation
Room 343/344 (New Orleans Convention Center )
Kory J. Priestley, NASA/LARC, Hampton, VA; and G. L. Smith and S. Thomas

In order to understand our climate, it is necessary to understand the energy flows which govern the movements and the temperatures of the atmosphere and oceans. The solar radiation absorbed by the Earth and its emission as outgoing longwave radiation (OLR) are the heat source and heat sink for this heat engine. The Clouds and Earth Radiant Energy System (CERES) Flight Model FM-1 and FM-2 sensors aboard the Terra and the FM-3 and -4 sensors aboard the Aqua spacecraft have provided the first CERES observed decadal Earth Radiation Climate Data Record (CDR). To assure continuity of this CDR the CERES FM-5 sensor will fly on the NPP spacecraft, scheduled for launch in October 2011. (Priestley et al., 2009).

The CERES sensors are scanning radiometers with three channels (Wielicki et al., 1996). The first is a shortwave channel for measuring sunlight reflected from the Earth, the second channel measures the total radiation (Reflected Solar + Emitted Thermal) from the Earth and a third channel measures thermal radiation emitted in the 8 to 12 micron window. Differencing the Shortwave and Total channels provides the broadband Outgoing Longwave Radiation. Onboard calibration is provided by internal calibration systems consisting of blackbodies for the Total and Window channels, by a shortwave incandescent calibration source for the Shortwave channel, and solar diffusers/attenuators for the Shortwave and Total channels. Each sensor undergoes a rigorous pre-launch characterization and calibration program at Northrop-Grumman's facilities in Redondo Beach, CA. The sensor Radiometric calibration is completed under simulated orbital conditions (under vacuum and anticipated thermal environments) utilizing Northrop-Grumman's Radiometric Calibration Facility which was specifically designed for the CERES program. The FM-5 sensor was built as part of the NASA EOS program in the late 1990's, originally completing the pre-launch calibration campaign in 1999 prior to being placed in storage while awaiting a mission assignment. In late 2006, the FM-5 sensor was removed form storage and completed abbreviated radiometric characterization tests to verify stability of performance. In 2008, the FM-5 sensor was assigned to the NPP mission and was removed form storage and the mechanical, thermal and electrical interfaces modified for integration on the NPP mission, and again subjected to the full pre-launch radiometric characterization campaign. The FM-5 was integrated to the NPP spacecraft in 2008 and has since undergone environmental and performance testing at the spacecraft level. During thermal-vacuum testing of NPP, the calibration of the FM-5 will be verified using the internal calibration systems to maintain traceability of the radiometric scale. At the time of the conference, the NPP with CERES FM-5 will have completed Thermal-vacuum testing, electromagnetic interference and compatibility testing and vibration and shock testing.

Approximately 30 days after NPP reaches operational orbit, the main contamination covers of FM-5 will be opened. This delay provide's adequate time for the spacecraft to complete outgassing, which could contaminate the optics of the CERES sensor. The Early Orbit Validation & Calibration campaign will commence once NPP reaches the operational orbit (Priestley et al., 2007). These tests will consist of exercising all operational modes of the sensor, characterizing scan angle dependent offsets, observing the onboard calibration sources to establish traceability to the pre-launch radiometric scale, as well as initiate the intercalibration opportunities with other CERES sensors which are operating on NASA's Terra and Aqua missions.

NPP will be placed in an orbit with the same inclination but higher altitude as the Aqua spacecraft and thus the CERES Aqua and CERES NPP sensors will make temporally, spatially and angularly matched radiance observations approximately every 72 hours as the orbits come into phase. In addition, the NPP orbit intersects that of the Terra spacecraft at 70oN on the day and 70oS on the night orbital passes respectively. Special operations will permit the comparison of FM-5 measurements with those from FM-1 and -2 aboard Terra.

To ensure the Sensor Data Record's (SDR's) meet performance requirements, the CERES Science Team's Instrument Working Group will implement an iterative approach of reprocessing the data twice to incorporate the results of a calibration protocol which has been developed over the course of the Terra and Aqua missions. At launch, the Raw Data Records (RDR's) will be processed to Edition_1CV SDR's using calibration coefficients determined during the pre-launch characterizations. Edition_1CV SDR's will contain fixed algorithms and coefficients, and serve as the input to the Cal/Val protocol, and thus be produced over the life of the mission. After a period of approximately six months, Edition_2 SDR's will be placed in production in parallel with the Edition_1 SDR's. In this edition, the calibration coefficients will be updated to account for any detected ground-to-flight shifts as well as begin accounting for any post-launch variability in the coefficients. Edition_2 SDR's will be the first ‘Science Quality' product which will be suitable for publication of scientific results. The Edition_2 SDR's will have a latency of approximately 6-months. After a period of 2-3 years, the Cal./Val protocol will be able to separate natural variability in the observations from small artifacts of sensor behavior which have temporal scales of months to years (e.g. those related to annual cycles of the spacecraft solar heating). At this time, the calibration coefficients will again be updated and incorporated in the Edition_3 SDR's which will be a re-processing of the SDR from the start of the mission. Edition_3 SDR's will meet the accuracy requirements for a Climate Data Record for Earth Radiation Budget.


Priestley, Kory J., G. Louis Smith, Susan Thomas and Grant Matthews: Validation Protocol for Climate Quality CERES Measurements, Proc. SPIE, 2007.

Priestley, K. J., G. L. Smith, B. A. Wielicki and N. G. Loeb: CERES FM-5 on the NPP spacecraft: Continuing the Earth radiation budget climate data record, SPIE 7474-12, 2009.

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. Met. Soc., 77, 853-868, 1996.

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