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Coefficient Changes   The relationship between the applied voltage and low and medium resolution etalons gap thickness is determined by a set of calibration coefficients. These have changed with time due to instrument malfunctions, temperature shocks, and long term instrument drifts. The list of the various sets used throughout the UARS mission is given below. Versions A-F were used in pre launch testing and are not included. Version G is rom resident. A change in coefficient set has the possibility of introducing an offset in the retrieved data. Although these artifacts have been largely removed from the data, the user should check the list if a discountinuity in the data is observed. Coefficient Version Start Date YYYY-MM-DD End Date YYYY-MM-DD Coefficient Set Description G 1991-07-19 1991-10-08 Coefficients at launch (ROM resident) H 1991-10-09 1991-10-11 I 1991-10-12 1991-11-01 J 1991-11-02 1992-04-06 First operational set of coefficients, corrects for launch shifts K 1992-04-07 1992-04-08 L 1992-04-09 1992-04-13 M 1992-04-14 1993-02-07 N 1993-02-08 1999-01-28 O 1999-01-29 1999-02-01 Bad set of coefficients; failed to incorporate voltage offset N 1999-02-02 1999-03-16 N/P 1999-03-17 1999-04-28 Cross calibration period. See Coefficent Cross calibration page for list of cross-calibration dates with version 'N'. P 1999-04-29 1999-12-16 Compensates for long-term instrument drift using calibration data from 31-Dec-1998. Q 1999-12-17 2000-03-28 Assumes an isothermal instrument at -8.5°C, but uses same coefficients as version 'P' R 2000-03-29 2000-05-09 Updates coefficients for current instrument temperature if the current temperature is valid, otherwise uses the last valid temperature; valid temperatures are assumed to be in the range -6°C and -12°C. Until a valid temperature is determined, a value of -8.5°C is used. N+ 2000-05-10 2000-05-13 Identical to version 'N' except that temperature control is applied as in version 'R'. R 2000-05-14 2000-12-17 S 2000-12-18 2001-05-05 Slight modification in the manner the reference temperature is determined from version 'R'. First the valid range is reduced to -7.5°C to -11.5°C. Second, since some invalid temperatures can fall within this range, the reference temperature is smoothed by: Tref = 0.1 Tread + 0.9 Told where Tref is the reference temperature to use, Told is the old reference temperature, and Tread is the current HRE temperature if it is in the valid range T 2001-05-06 2002-05-05 Same as version 'S' except this version checks the lamp status bits to determine if the temperature is valid. No more than 1 lamp can be physically on at any time, so a bit pattern that corresponds to more than one lamp on indicates that the subcom is no good, and the temperature cannot be trusted. G 2002-05-06 2002-05-06 Incomplete microload during restart resulted in using ROM-resident coefficients. T 2002-05-07 2005-04-30 Coefficient set used through end of mission.

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