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Program ID 6928: GHRS Cycle 6: NoCo Special Sensitivity Measurement without the COSTAR Mirrors

Purpose: The purpose of this test is to determine the degree to which the COSTAR mirrors have reduced the throughput of the GHRS, particularly at wavelengths below Lyman-alpha.

Description: This test will observe two ultraviolet standard stars at a series of wavelengths. Both stars will be observed shortly before the COSTAR mirrors are withdrawn (within 10 days), as well as within the brief interval between that withdrawal and the Servicing Mission. Two stars are observed in order to provide some redundancy for a set of observations that are impossible to repeat.

The wavelengths have been chosen to emphasize those below about 1200 Å, where the greatest decline in sensitivity has been seen since SMOV. However, the usual series of wavelengths on both Side 1 and Side 2 will be observed so that this program is also a sensitivity monitor close-out. In this case, we will also obtain images of the Large Science Aperture after the acquisition has been made, so that we can verify the quality of the pointing after the fact.

This test will execute once only during Cycle 6, at the end of the Cycle.

Fraction of GO Programs Supported: This test is primarily of benefit to understanding overall telescope performance and is not strictly relevant to GO programs.

Resources:

Observation: External-8 orbits.

Analysis: 0.30 FTE. These observations will require a straightforward interpretation on their own part, but considerable preparation is needed to ensure successful execution. Also, we will need to carefully consider how these new data compare to older sensitivity tests.

Special Requirements: The pre-SMOV aperture locations will need to be loaded into the PDB for this to execute. This will be done by O. Lupie.

Accuracy: We expect relative accuracy of 2% or better.

Products: An ISR.