Pamela Barry

Hyperion on-orbit validation of spectral calibration using atmospheric lines and an on-board system

The Hyperion instrument mounted on the EO-1 spacecraft was launched November 21, 2000 into an orbit following LANDSAT-7 by 1 minute. Hyperion has a 7.5 km swath width, a 30 meter ground resolution and 220 spectral bands. Its spectral bands extend from 400 nm to 2500 nm with each band having about a 10 nm bandwidth. A unique process to validate the spectral calibration was developed. The process was based on an atmospheric limb collect and supported with a solar calibration collect. The data contained a collection of solar lines, atmospheric lines and absorption lines from the paint that coats the solar calibration reflectance panel. Correlating the positions of these lines with reference data, the center wavelength of each pixel across the field of view for the VNIR and SWIR spectral regions of the imaging spectrometer has been verified. In this paper we discuss the data collection and the technique applied to the VNIR and SWIR focal plane array.

Measurement of Hyperion MTF from on-orbit scenes

The Hyperion instrument was launched November 21, 2000 mounted on the EO-1 spacecraft into orbit 1 minute behind Landsat-7. Hyperion has a 7.5 km swath width, a 30 meter ground sample distance (GSD) and more than 220 spectral bands. Part of the on-orbit characterization involves MTF measurements from several ground scenes. These scenes included edges from the moon and glaciers as well as several bridges. The scenes were processed to determine the MTF for both the Visual Near InfraRed (VNIR) and Short-wave InfraRed (SWIR) imaging spectrometers and were compared to measurements made prior to launch.

Aggregation of Hyperion hyperspectral spectral bands into Landsat-&ETM+ spectral bands

The Landsat 7 ETM+ spectral bands centered at 479 nm, 561 nm, 661 nm and 834 mn (Bands 1, 2, 3, and 4) fall nicely across the Hyperion VNIR hyperspectral response region. They have bandwidths of 67 nm, 78 nm, 60 nm and 120 nm, respectively. The Hyperion spectral bandwidth of 10.2 nm results in 10 to 15 Hyperion spectral samples across each Landsat band in the VNIR. When the Hyperion spectral responses in the 10.2 nm bands are properly weighted to aggregate to a given Landsat band, the radiometric response of the Landsat band can be reproduced by Hyperion. This is done for Bands 2, 3 and 4 on the scene 7 of Lake Frome, Australia collected simultaneously by Hyperion and Landsat on January 21, 2001. The initial comparison of the radiances from Hyperion synthesized into the ETM+ bands with the Landsat-7 ETM+ radiances showed differences of 15-23%, with ETM+ being higher. Prior to launch a laboratory standard comparison showed differences of 10-13% in the same direction.

Radiometric calibration validation of the Hyperion instrument using ground truth at a site in Lake Frome, Australia

The Hyperion instrument mounted on the EO-1 spacecraft was launched November 21, 2000 into an orbit following LANDSAT-7 by 1 minute. Hyperion has a 7.5 km swath width, a 30 meter ground resolution and 10 nm spectral resolution extending from 400 nm to 2500 nm. The first portion of the mission was used to measure and characterize the on-orbit radiometric, spectral, image quality and geometric performance of the instrument. Lake Frome, a dry salt lake in South Australia was chosen as a calibration site for Hyperion. Surface spectral data were collected along a transect through the center of the lake prior to the Hyperion overpass. This paper discusses the incorporation of the Lake Frome ground measurements and analysis into the performance verification of the instrument.

On-orbit solar radiometric calibration of the Hyperion instrument

The end-to-end calibration plan for the Hyperion EO-1 hyperspectral payload is presented. The ground calibration is traceable to a set of three high quantum efficiency p-n silicon photodiode trap detectors the responsivities of which are traceable absolutely to solid state silicon diode physical laws. An independent crosscheck of the radiance of the Calibration Panel Assembly used to flood the Hyperion instrument in field and aperture was made with a transfer radiometer developed at TRW. On-orbit measurements of the suns irradiance as it illuminates a painted panel inside the instrument cover are compared to the radiance scale developed during pre-flight calibration. In addition, an on-orbit calibration lamp source is observed to trace the pre-flight calibration constants determined on the ground to the solar calibration determination.

Hyperion data collection: Performance assessment and science application

The EO-1 spacecraft, part of the new millennium program, hosts three advanced technologies, the Hyperion imaging spectrometer, the advanced land imager (ALI), and the LEISA atmospheric corrector (LAC) payloads. EO-1 was launched on November 21, 2000 into a sun synchronous orbit behind Landsat 7. Hyperion, which has a 7.6 km swath width, a 30 meter ground resolution and 220 spectral bands, is the focus of this paper. The calibrated spectral bands extend from 400 mn to 2400 mn in 10 mn bandwidths. The initial objectives for the TRW Hyperion team was to characterize the on-orbit performance as thoroughly as possible and to compare with pre-flight characterization test data. On-orbit characterization was followed by research activities carried out by the EO-1 science validation team aimed at assessing the utility of space-based hyperspectral data. This paper provides an overview of the technical innovation and on-orbit characterization of the Hyperion instrument. This paper highlights data collects and analysis methodology of a set of standard and unique data collects that were defined to address specific issues. Sample science applications are also briefly discussed.

Aggregation of Hyperion hyperspectral spectral bands into Landsat-7 ETM+ spectral bands

The LANDSAT-7 ETM+ spectral bands centered at 479nm, 561 nm, 661 nm and 834 nm (bands 1, 2, 3, and 4) fall nicely across the Hyperion VNIR hyperspectral response region. They have bandwidths of 67nm, 78nm, 60 nm and 120 nm, respectively. The Hyperion spectral bandwidth of 10.2 nm results in 10 to 15 Hyperion spectral samples across each Landsat band in the VNIR. When the Hyperion spectral responses in the 10.2 nm bands are properly weighted to aggregate to a given Landsat band, the radiometric response of the Landsat band can be reproduced by Hyperion. Landsat bands 5 and 7 centered at 1650 and 2207 nm (with bandwidths of 190 and 250 nm respectively) fall in the Hyperion SWIR spectral response region. Hyperion spectral response for one area of a scene in Railroad Valley, NV on May 13, 2001 has been binned into Landsat bands and compared with Landsat values collected at the same time.

Use of the Lake Frome ground truth campaign as a cross-calibration of the Hyperion instrument

The Hyperion imaging spectrometer instrument was launched on the EO-1 spacecraft on November 24, 2000 into an orbit trailing Landsat 7 by one minute. Hyperion has a 7.5 km swath width, a 30 meter ground resolution and 10 nm spectral resolution. The first portion of the mission was used to measure and characterize the on-orbit radiometric, spectral, image quality and geometric performance of the instrument. Ground images were specifically collected for this characterization. This paper discusses the incorporation of a vicarious calibration site, Lake Frome in Australia, into the performance verification of the instrument. Coordination with CSIRO during a ground truth campaign resulted in image data collection on Hyperion over flights on December 20, 2000 and January 5 and 21, 2001 and provided an opportunity to compare predicted top of the atmosphere radiance from various sites at the time of the overpass for cross-calibration.

On-orbit spectral calibration verification of Hyperion

On November 21, 2000, NASA launched the EO-1 satellite, carrying the Hyperion hyperspectral imager, into an orbit precisely following LANDSAT-7 by 1 minute. Hyperion has a 7.5 km swath width, a 30 meter ground resolution and 220 spectral bands. Its spectral bands extend from 400 nm to 2500 nm with each band having about a 10 nm bandwidth. A unique process to validate the spectral calibration that is based on an the atmospheric limb data collect has been developed. The data contained a collection of solar lines, atmospheric lines and absorption lines from the paint which coats the solar calibration reflectance panel. Correlating the positions of these lines with reference data, the center wavelength of each pixel across the field of view for the SWIR spectral regions of the imaging spectrometer has been verified. In this paper we discuss the data collection and the technique applied to the SWIR focal plane array.

On-orbit radiometric calibration the Hyperion instrument

The end-to-end calibration plan for the Hyperion EO-1 hyperspectral payload is presented. The ground calibration is traceable to a set of three high quantum efficiency p-n silicon photodiode trap detectors the responsivities of which are traceable absolutely to solid state silicon diode physical laws. An independent crosscheck of the radiance of the Calibration Panel Assembly used to flood the Hyperion instrument in field and aperture was made with a transfer radiometer developed at TRW. On-orbit measurements of the Suns irradiance as it illuminates a painted panel inside the instrument cover are compared to the radiance scale developed during ground calibration. In addition, an on-orbit calibration lamp source is observed to trace the ground calibration constants determined on the ground to the solar calibration determination. Reference is made to a ground truth campaign at Lake Frome, Australia and a Landsat radiometric comparison.