As described in Section 4.1.6
, gain sag is beginning to affect spectra obtained with the FUV detector. To address this problem the COS team performed studies to move the Aperture Mechanism so that the FUV spectra fall on a different part of the detector, called a lifetime position. This work is divided into three phases. Table 12.4
lists the programs that were used to determine the location of the new lifetime position, enable science at that location, and finally calibrate observations obtained there. The additional lifetime calibration program “Second COS FUV Lifetime Position: Wavelength Scales (FCAL1)” uses observations from programs 12805, 12806, and 12796.