SIM Version 17: (14 May 2009):Version 17 consists of SORCE SIM data with the revised degradation corrections that corrects an over-estimate of the degradation apparent in the data from December 2007 to the present time. Additionally, this version improves the irradiance discontinuities caused by the two SORCE OBC (on-board computer) resets that occurred on May 23, 2007 and on the January 3 2009. The two month period from 2007/05/23 to 2007/07/23 has a somewhat lower precision due to a very slow and small relaxation in the gamma_z parameter caused by the resultant cold temperatures caused by the OBC anomaly. There is currently insufficient data to see if this is also true for the second OBC event. The gamma_z parameter defines the relative orientation of the prism to the CCD drive system's steering mirror ( see Harder et al., Solar Physics (2005) 230: 141-167 for more detail on the operation of the drive). The effect of the change in gamma_z is to change the wavelength grid spacing between successive spectral samples this generates a small discontinuity when the data is re-sampled onto a standard wavelength grid.
Note: (5 February 2009):Spectral irradiance data from the SORCE SIM instrument after 3 January 2009 to present are currently unavailable. The cold instrument temperatures experienced during the spacecraft anomaly (over the period of 4-13 January 2009) produced a small, but noticeable, wavelength shift in the data. An improved correction has been developed for the prism drive parameters and will be applied soon.
SIM Version 16 (22 August 2008):This release of the SIM data products uses updated degradation calibration.
The SIM data after 15 February 2008 use an extrapolated degradation correction that tends to show a fall off in the irradiance faster than what it ought to be. This effect is most noticeable in the visible portion of the spectrum, and is less apparent in the infrared where the degradation is small. Eight to ten months of data are need to correct the degradation, so this problem will be corrected later this year.
SIM Version 15 (28 November 2007):
The SORCE onboard computer (OBC) anomaly in May 2007 introduced a small wavelength shift in the SIM spectral data. A new calibration corrects this problem.
Note: (6 June 2007):Spectral irradiance data from the SORCE SIM instrument from 14 May 2007 to present are currently unavailable. The cold instrument temperatures experienced during the spacecraft anomaly (over the period of 14-20 May 2007) produced a small, but noticeable, wavelength shift in the data that will require a re-analysis of the currently used prism drive parameters. Data from SIM since reactivation of the instruments is currently being processed and analyzed to ensure that shift is not transient in nature; a new data version that corrects this wavelength shift will be made publicly available as soon as the drive parameter changes have been verified. Since the wavelength shift is small, interim SIM data for this period is available through the instrument scientists. Please contact us for the data and caveats on its usage if needed.
SIM Version 12 (28 February 2007):The following calibration and processing code changes have been implemented for the release of SIM version 12 data. These changes have resulted in irradiance corrections of approximately 1% for the shorter wavelengths, and 0.3-0.5% for long wavelengths (850-1600 nm), along with an extended time and wavelength range of available SIM data.
- Updated prism degradation based on SIM A/B comparisons (kappa & column). Further refinements have been identified and will be implemented in the next release.
- Extended time range for SIM data: mission day 189 (1 August 2003) to present.
- Updated shift algorithm for first year data. Dropped use of Vis2 diode due to detector degradation and the difficulty of making the needed corrections.
- Code updates and corrections to properly calculate and propagate errors through processing.
- Updated reference spectra for canonical mission day 453 (21 April 2004).
- New spectral coverage for diodes and ESR.
- Vis1: 310-900 nm
- IR: 900-1600 nm
- ESR: 1600-2400 nm