24/10/2006 Dr. J.J. Remedios, GIST 2006 1

GERB Spectral Calibration

Nick Nelms1*, Oliver Blake1, Jacqui Russell2, John Remedios1,

1SRC, Physics and Astronomy, University of Leicester, U.K.

2Imperial College, U.K.

*Now at ESTEC, Netherlands, U.K.

http://www.leos.le.ac.uk/

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Leicester Spectral Calibration Facility

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LSCF Operations1. Reference detectors (Si detector and pyranometer) calibrated at

NPL.

2. Use 9 GERB pixels to map entire beam shape as reference detector is much larger than a GERB pixel.

3. N.B. Beam shape is a function of wavelength.

4. Move 8 GERB pixels at a time into a given position in the beam (32 measurements to cover array).

5. Data recorded in LSCF, analysed at Imperial College

6. Difficulties: Source variability in the shortwave. Low signals in the longwave and hence takes a long time to do measurements.

7. Reference detector calibrations ideally need to be re-done.

8. GERB4 FM calibrations nearly completed (this week). Flight spare next.

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Results I

Data recorded by Oliver Blake, LUPlots by Jacqui Rusell, Imperial College

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Results II

Data recorded by Oliver Blake, LUPlots by Jacqui Rusell, Imperial College

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Results III

Data recorded by Oliver Blake, LUPlots by Jacqui Rusell, Imperial College

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Schedule (October 19th)

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Conclusions and Future outlook

• Current calibration methodology successful in terms of mapping out pixel response of GERB linear array.

• Shortwave measurements limited to 0.33 microns because of source strength decrease towards 0.3 microns

• Infra-red signal-to-noise challenging. More limited pixel variability information may be the result.

• Will extend measurements to 20 microns.

Future outlook1. Linearity tests. The delivery of GERB 4 FM FPA.2. Window transmission responses.3. Reference detector overlap measurements.4. Humidity tests5. Two more GERB focal plane calibrations.