1. GERB in-flight calibration Monitoring Instrument Gain

2. In-flight Gain

3. Gain vs detector temperature

4. Variation of black body and detector temperatures Detector temp. variation 0.4  C Implies G(TOT) variation ~ 0.008 (0.04%)

5. Black body – space (offset) voltage V space -V IBB

6. Black body – space (offset) voltage

7. GERB - equinox stray light contamination

8. Black body – space (offset) voltage

9. Variation of pixel gains

10. Gain variations 28/4/03 – 03/03/04 pixel 20 MEAN: 16.9 SD: 0.4% pixel 70 MEAN: 18.0 SD: 0.4% pixel 120 MEAN: 19.1 SD: 0.4% pixel 180 MEAN: 19.1 SD: 0.4% pixel 240 MEAN: 17.3 SD: 0.4%

11. Gain variations 28/4/03 – 03/03/04 Pixel 123 (noisy)

12. Gain variations Scan means 28/4/03 – 03/03/04

13. Gain variations 28/4/03 – 03/03/04

14. ~2% change

15. Gain variations Scan means 28/4/03 – 03/03/04

16. Gain variations NANRG product November 2003

17. 2 SD of mean 3 SD of mean 4 SD of mean

18. Variation of offset across a scan

19. In-orbit calibration G ~ 20  V ~ 40 implies  L ~ 2Wm -2 sr -1 (c.f. 3Wm -2 sr -1 )

20. Summary Instrument gains show variation with temperature of internal black body or environmental conditions, aside an expected (very small) dependence on detector temperature Over 11 months standard deviation of the gains calculated from single scans are around 0.15% Variation of gain calculated for the data products shows a number of outliers due to stray light or moon contamination – changing to offline gain calculation could eliminate this

21. Summary Stray light contamination in the internal black body results in a problem of offset subtraction This could be eliminated by using a neighbouring measurement of the internal black body – further study to fully characterize the extent of the stray light and the offset variation is required first.