Chapter 4:
Cycle 21 Scientific Instruments

4.1 Advanced Camera for Surveys (ACS)

4.2 Wide Field Camera 3 (WFC3)

4.3 Fine Guidance Sensor (FGS)

4.4 Cosmic Origins Spectrograph (COS)

Far-Ultraviolet Channel (COS/FUV)

Near-ultraviolet Channel (NUV)

COS FUV XDL Gain Sag

Optimizing the Science Return of COS

4.5 Space Telescope Imaging Spectrograph (STIS)

Summary of STIS changes after SM4

4.6 Additional Observing Modes

4.6.1 Imaging Polarimetry

4.6.2 Slitless Imaging Spectroscopy

4.6.3 Ramp and Quad Filters

4.6.4 Coronagraphy

4.6.5 Observations with Two Instruments - Parallel Observing

4.7 Instrument Comparisons

4.7.1 HST Imaging

4.7.2 Spectrographs