A new version of the ETC (20.1.1) was released on January 26, 2012. This version contains COS-only related updates and affects proposers using COS for Cycle 20 proposals:
Throughputs of all FUV gratings have been updated to take into account that the sensitivity of the FUV channel is currently decreasing at substantially higher rates than before. The new throughputs are projected to January 1, 2013.
These new projections may increase the required time to reach a certain S/N by as much as 50%. Users are strongly recommended to repeat any calculations performed in preparation for the Cycle 20 call for proposals with the new version of the ETC.
- The throughput of the G285M/NUV grating was also updated at this time. While there has been no change in the slope of the sensitivity decline, which is ~11% per year, this throughput had not been updated in the last two years, leading to exposure times that would be underestimated by ~25% by the middle of Cycle 20. Users proposing for Cycle 20 with the G285M grating should also update their calculations by using the new version of the ETC.
- A software bug in the ETC algorithm that simulates dispersed light target acquisitions (for both FUV and NUV) resulted in overestimated exposure times for a certain S/N, by as much as a factor of 2. Users proposing for Cycle 20 are strongly encouraged to redo their calculations with the new version of the ETC.