Dr. Peter L. Spence Profile

Dr. Peter L. Spence

Atmospheric Scientist at Science Applications International Corp

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Publications (12)

Proceedings Article | 22 August 2005 Paper

Z-domain numerical filter for removal of thermistor bolometer slow mode transients

Grant Matthews, Kory Priestley, Peter Spence

Proceedings Volume 5882, 588213 (2005) https://doi.org/10.1117/12.613981

KEYWORDS: Sensors, Bolometers, Optical filters, Neodymium, Calibration, Wheatstone bridges, Electronic filtering, Clouds, Thermal modeling, Signal detection

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Proceedings Article | 22 August 2005 Paper

Compensation for spectral darkening of short wave optics occurring on the cloud's and the Earth's radiant energy system

Grant Matthews, Kory Priestley, Peter Spence, Denise Cooper, Dale Walikainen

Proceedings Volume 5882, 588212 (2005) https://doi.org/10.1117/12.618972

KEYWORDS: Lamps, Climatology, Optical filters, Calibration, Satellites, Ultraviolet radiation, Clouds, Ocean optics, Sensors, Space telescopes

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Cloud's and the Earth's Radiant Energy System (CERES) is an investigation into the role of clouds and radiation in the Earth's climate system. Four CERES scanning thermistor bolometer instruments are currently in orbit. Flight model 1 (FM1) and 2 (FM2) are aboard the Earth Observing System (EOS) Terra satellite and FM3 and FM4 are aboard the EOS Aqua satellite. Each CERES instrument measures in three broadband radiometric regions: the shortwave (SW 0.3-5μm), total (0.3- > 100μm), and window (8-12μm). It has been found that both CERES instruments on the Terra platform imply that the SW flux scattered from the Earth had dropped by up to 2% from 2000 to 2004. No climatological explanation for this drop could be found, suggesting the cause was a drift in both the Terra instruments. However, the onboard calibration lamps for the SW channels do not show a change in gain of this magnitude. Experience from other satellite missions has shown that optics in the orbital environment can become contaminated, severely reducing their transmission of ultra-violet (UV) radiation. Since the calibration lamps emit little radiance in the UV spectral region it was suggested that contaminates could be responsible for an undetectable 'spectral darkening' of the CERES SW channel optics and hence the apparent drop in SW flux. Further evidence for this was found by looking at the comparison between simultaneous measurements made by FM1 and FM2. The proposed mechanisms for contaminant build up would not apply to a CERES instrument operating in the normal cross track scan mode. Indeed it was found from the comparison between CERES instruments on Terra that the response of the instrument operating in rotating azimuth plane (RAPS) mode consistently dropped relative to the other cross track instrument. Since at all times one of the instruments operates in cross track mode, where it is not subject to spectral darkening, it allowed that unit to be used as a calibration standard from which the darkening of the other RAPS instrument can be measured. A table of adjustment coefficients to compensate for this spectral darkening are therefore derived in this paper. These figures are designed to be multiplied by SW fluxes or radiances produced in the climate community using Edition 2 CERES data. SW CERES measurements that have been revised using these coeffcients are therefore to be referred to as ERBE-like Edition2_Rev1 or SSF Edition2B_Rev1 data in future literature. Current work to fully characterize the effect of spectral darkening on the instrument spectral response before the release of Edition 3 data is also described.

Proceedings Article | 26 October 2004 Paper

Performance results of CERES instrument sensors aboard EOS Terra and Aqua spacecraft using tropical ocean measurements

Susan Thomas, Kory Priestley, Peter Spence

Proceedings Volume 5542, (2004) https://doi.org/10.1117/12.560961

KEYWORDS: Sensors, Shortwaves, Calibration, Space operations, Clouds, Satellites, Instrument modeling, Earth's atmosphere, Sun, Phase modulation

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Proceedings Article | 26 October 2004 Paper

Correction of drifts in the measurements of the Clouds and the Earth's Radiant Energy System scanning thermistor bolometer instruments on the Terra and Aqua satellites

Peter Spence, Kory Priestley, Edward Kizer, Susan Thomas, Denise Cooper, Dale Walikainen

Proceedings Volume 5542, (2004) https://doi.org/10.1117/12.560992

KEYWORDS: Sensors, Shortwaves, Clouds, Satellites, Calibration, Bolometers, Data corrections, Software development, Sun, Optical filters

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Proceedings Article | 10 November 2003 Paper

A comprehensive radiometric validation protocol for CERES Earth Radiation Budget climate record sensors

Kory Priestley, Susan Thomas, Peter Spence, Z. Szewczyk, Edward Kizer, Dale Walikainen, Aiman Al-Hajjah, Robert Wilson

Proceedings Volume 5151, (2003) https://doi.org/10.1117/12.507520

KEYWORDS: Calibration, Sensors, Optical filters, Shortwaves, Clouds, Space operations, Instrument modeling, Environmental sensing, Climatology, Error analysis

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Proceedings Article | 10 November 2003 Paper

Three-channel intercomparison and direct comparison on-orbit stability analyses as applied to the CERES instruments on the Terra and Aqua satellites

Peter Spence, Kory Priestley, Edward Kizer, Dale Walikainen, Susan Thomas

Proceedings Volume 5151, (2003) https://doi.org/10.1117/12.507540

KEYWORDS: Sensors, Shortwaves, Calibration, Satellites, Clouds, Software development, Bolometers, Optical filters, Climatology, Instrument modeling

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Proceedings Article | 10 November 2003 Paper

Geolocation validation of CERES instruments using radiance measurements

Peter Spence, Phillip Hess, Kory Priestley

Proceedings Volume 5151, (2003) https://doi.org/10.1117/12.506073

KEYWORDS: Error analysis, Satellites, Sensors, Clouds, Detection and tracking algorithms, Bolometers, Shortwaves, Space operations, Solar radiation, Logic

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Proceedings Article | 14 March 2003 Paper

Performance studies of CERES sensors on Earth Science Enterprise (ESE) Terra mission using onboard calibrations and other validation methods

Susan Thomas, Kory Priestley, Robert Lee, Peter Spence, Robert Wilson, Aiman Al-Hajjah, Jack Paden, Dhirendra Pandey

Proceedings Volume 4886, (2003) https://doi.org/10.1117/12.462968

KEYWORDS: Sensors, Shortwaves, Calibration, Black bodies, Mirrors, Bolometers, Space operations, Sensor calibration, Diffusers, Space telescopes

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Clouds and the Earth's Radiant Energy system (CERES) sensors provide accurate measurements for the long-term monitoring of the Earth's radiation budget components such as reflected shortwave and emitted longwave radiances. CERES instruments has three scanning thermistor bolometers that measure broadband radiances in the shortwave (0.3 to 5.0 micrometer), total (0.3 to >100 micrometer) and in 8 - 12 micrometer water vapor window regions. Two of the CERES instruments (Flight Models 1 and 2(FM1&2)) are part of ESE Terra mission and has been successfully making Earth radiance measurements for the past two years. The CERES sensors are calibrated in flight using the on-board blackbody sources and a tungsten lamp known as internal calibration module (ICM) as well as a solar diffuser plate known as the Mirror Attenuator Mosaic (MAM). The ICM calibrations is used to determine the sensor measurement precisions during the ground, ground to orbit, and the on-orbit phases of the sensor calibrations. The MAM calibrations define on-orbit shifts or drifts in shortwave and total sensor responses. The traditional validation studies conducted to understand the stability of the sensors' performance include the analysis of Tropical Mean (TM) value using nadir tropical ocean measurements and three channel intercomparison between sensors of the same instrument. With two CERES instruments on the same platform, an additional study utilizing direct comparison of similar sensor measurements viewing the same geolocation is also conducted. The ICM results have shown that total sensors on both instruments have shown a variation of 0.25 and 0.5 percent respectively, whereas the shortwave sensors show a minimal change of 0.2 percent each. With high variability during the initial year, the MAM results have stabilised within the 0.5 percent precision range in the second year. The validation studies have shed additional light into the behaviour of total sensors in the shortwave and longwave spectral regions. The TM longwave day night difference (DN) derived from longwave sensors of each CERES instrument indicate that the FM1 sensors have varied about 0.25 watts m^-2sr^-1, whereas the total sensor in FM2 has a gradual rise of 1.4 watts m^-2sr^-1 in a 30 month period. This paper discusses briefly the contribution of each calibration and validation study in understanding the CERES sensors' behavior and the results from both Terra instruments' sensors. It also discusses how the various analyses are put together in understanding the rise seen in the total sensor of FM2 instrument.

Proceedings Article | 24 September 2002 Paper

In-flight stability analyses applied to the Clouds and the Earth's Radiant Energy System scanning thermistor bolometer instruments on the Terra satellite

Peter Spence, Kory Priestley, Susan Thomas

Proceedings Volume 4814, (2002) https://doi.org/10.1117/12.451695

KEYWORDS: Shortwaves, Sensors, Clouds, Satellites, Calibration, Linear filtering, Bolometers, Optical filters, Image filtering, Analytical research

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Proceedings Article | 21 February 2001 Paper

Relationship between the Clouds and the Earth's Radiant Energy System (CERES) measurements and surface temperatures of selected ocean regions

Dhirendra Pandey, Robert Lee, Shannon Brown, Jack Paden, Peter Spence, Susan Thomas, Robert Wilson, Aiman Al-Hajjah

Proceedings Volume 4150, (2001) https://doi.org/10.1117/12.416957

KEYWORDS: Optical filters, Shortwaves, Satellites, Clouds, Temperature metrology, Sensors, Calibration, Bolometers, Sensor calibration, Space telescopes

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Proceedings Article | 9 February 2001 Paper

Broadband measurements of lunar radiances using the Tropical Rainfall Measuring Mission (TRMM) spacecraft/Clouds and the Earth's Radiant Energy System (CERES) sensors

Robert Lee, G. Louis Smith, Peter Spence, Dale Walikainen, Zbigniew Szewczyk, Jack Paden, Kory Priestley

Proceedings Volume 4169, (2001) https://doi.org/10.1117/12.417128

KEYWORDS: Sensors, Shortwaves, Space operations, Calibration, Bolometers, Image sensors, Clouds, Lamps, Mirrors, Black bodies

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12 Currently, the moon is being used as a radiometric target to determine on-orbit relative shifts or shifts in the responses of certain spacecraft shortwave sensors. Along these lines, the 1998 Tropical Rainfall Measuring Mission (TRMM) Spacecraft/Clouds and the Earth's Radiant Energy System (CERES) thermistor bolometer sensor observations of lunar radiances were analyzed to evaluate the feasibility using the lunar radiances to calibrate the CERES sensor responses. Over a 5 to 110 degree phase angle range, the CERES sensors were used to measure: broadband shortwave (0.3 micrometers to 5.0 micrometers ) moon-reflected solar filtered radiances; broadband total (0.3 micrometers to more than 100 micrometers ) moon- reflected solar and moon-emitted longwave filtered radiances; and narrowband window (8 micrometers to 12 micrometers ) moon- emitted longwave filtered radiances. The TRMM/CERES on-orbit radiance measurements are tied to an International Temperature Scale of 1990 (ITS-90) modeled radiometric scale at uncertainty levels approaching 0.2% (0.2 Wm^-2sr^-1). Therefore, the TRMM/CERES measurements should be useful in forecasting the precisions of scheduled CERES lunar measurements from the NASA Terra and Aqua Spacecraft platforms near phase angle of 22 and 55 degrees, respectively. The 7-degree phase angle, 1998 CERES shortwave, total, and window measurements yielded lunar filtered radiances of approximately 4.5+/- 0.2, 24.4+/- 0.5, and 4.5+/- 0.2 Wm^-2sr^-1, respectively. These lunar measurements indicate that broadband shortwave radiances can be characterized at the 5% uncertainty range. The 7-degree, shortwave lunar radiances were found to be approximately 1.5 and 3 times brighter greater the corresponding radiances found at the 22-degree and 55-degree phase angles, respectively. Therefore, the Terra and Aqua CERES lunar shortwave measurements near 22.5- degree and 55-degree phase angles should yield projected precisions in the 7% and 15% range, respectively. The CERES lunar filtered radiance are presented and discussed. Research efforts are outlined briefly for comparing the total sensor broadband and window narrowband longwave lunar radiances during the January 9, 2001 lunar eclipse.

Proceedings Article | 15 November 2000 Paper

Determination and validation of slow mode coefficients of the Clouds and the Earth's Radiant Energy System (CERES) scanning thermistor bolometers

G. Louis Smith, Dhirendra Pandey, Peter Spence, Kory Priestley, Bruce Barkstrom, Robert Lee, Jack Paden, Susan Thomas, Robert Wilson, Aiman Al-Hajjah

Proceedings Volume 4135, (2000) https://doi.org/10.1117/12.494226

KEYWORDS: Sensors, Calibration, Shortwaves, Bolometers, Black bodies, Space operations, Clouds, Instrument modeling, Aerospace engineering, Fermium

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