9.3 Spectral Element Movement Overheads
For any COS exposure, including target-acquisition exposures, any change of spectral elements incurs an overhead. A transition from FUV to NUV requires movement of OSM1 to the NCM1 position, followed by a possible OSM2 movement. On the other hand, a transition from NUV to FUV requires only the movement of OSM1 from NCM1 to the desired FUV grating and cenwave. Table 9.3 gives the times required for movement between OSM1 spectral elements. These depend mildly on cenwave, so typical values are shown. Table 9.4 gives the times for movement between OSM2 spectral elements. These do not depend on cenwave.
All COS visits start with OSM1 at the G130M position (with central wavelength 1291 Å) and OSM2 at the MIRRORA
position. These gratings are highlighted in Table 9.3 and Table 9.4. OSM1 and OSM2 move sequentially, so the total overhead is the sum of the two separate overheads. The time required to move from one optical element to another is independent of the FP-POS
settings.
Table 9.3: Overhead Times for Motions Between OSM1 Spectral Elements.
Movement time(s) from | to G140L | to G130M1 | to G130M | to G160M | to NCM1 |
---|---|---|---|---|---|
G140L | — | 194 | 165 | 205 | 114 |
G130M1 | 198 | — | — | 156 | 158 |
G130M | 172 | — | — | 117 | 119 |
G160M | 212 | 162 | 122 | — | 165 |
NCM1 | 120 | 154 | 121 | 159 | — |
1 Use these entries if the G130M cenwave is 1055 or 1096.
Table 9.4: Overhead Times for Motions Between OSM2 Spectral Elements.
Movement time(s) from | to G230L | to G185M | to G225M | to G285M | to MIRRORA | to MIRRORB |
---|---|---|---|---|---|---|
G230L | — | 210 | 141 | 176 | 105 | 99 |
G185M | 204 | — | 136 | 102 | 170 | 176 |
G225M | 136 | 141 | — | 107 | 101 | 107 |
G285M | 170 | 108 | 102 | — | 136 | 142 |
| 100 | 175 | 106 | 141 | — | 71 |
| 94 | 181 | 112 | 147 | 77 | — |
-
COS Instrument Handbook
- Acknowledgments
- Chapter 1: An Introduction to COS
-
Chapter 2: Special Considerations when Observing with COS
- • 2.1 COS FUV Detector Lifetime Positions
- • 2.2 Visit Length
- • 2.3 Central Wavelength Settings Added in Cycle 26
- • 2.4 ORIENT constraints for Extended Sources
- • 2.5 COS Observations Below 1150 Angstroms: Resolution and Wavelength Calibration Issues
- • 2.6 Time-Dependent Sensitivity Changes
- • 2.7 Spectroscopic Use of the Bright Object Aperture
- • 2.8 Non-Optimal Observing Scenarios
- • 2.9 NUV Spectroscopic Acquisitions
- • 2.10 SNAP, TOO, and Unpredictable Source Programs with COS
- • 2.11 Choosing between COS and STIS
- Chapter 3: Description and Performance of the COS Optics
- Chapter 4: Description and Performance of the COS Detectors
-
Chapter 5: Spectroscopy with COS
- • 5.1 The Capabilities of COS
- • 5.2 TIME-TAG vs. ACCUM Mode
- • 5.3 Valid Exposure Times
- • 5.4 Estimating the BUFFER-TIME in TIME-TAG Mode
- • 5.5 Spanning the Gap with Multiple CENWAVE Settings
- • 5.6 FUV Single-Segment Observations
- • 5.7 Internal Wavelength Calibration Exposures
- • 5.8 Fixed-Pattern Noise
- • 5.9 COS Spectroscopy of Extended Sources
- • 5.10 Wavelength Settings and Ranges
- • 5.11 Spectroscopy with Available but Unsupported Settings
- Chapter 6: Imaging with COS
- Chapter 7: Exposure-Time Calculator - ETC
-
Chapter 8: Target Acquisitions
- • 8.1 Introduction
- • 8.2 Target Acquisition Overview
- • 8.3 ACQ SEARCH Acquisition Mode
- • 8.4 ACQ IMAGE Acquisition Mode
- • 8.5 ACQ PEAKXD Acquisition Mode
- • 8.6 ACQ PEAKD Acquisition Mode
- • 8.7 Exposure Times
- • 8.8 Centering Accuracy and Data Quality
- • 8.9 Recommended Parameters for all COS TA Modes
- • 8.10 Special Cases
- Chapter 9: Scheduling Observations
- Chapter 10: Bright-Object Protection
- Chapter 11: Data Products and Data Reduction
-
Chapter 12: The COS Calibration Program
- • 12.1 Introduction
- • 12.2 Ground Testing and Calibration
- • 12.3 SMOV4 Testing and Calibration
- • 12.4 COS Monitoring Programs
- • 12.5 Cycle 17 Calibration Program
- • 12.6 Cycle 18 Calibration Program
- • 12.7 Cycle 19 Calibration Program
- • 12.8 Cycle 20 Calibration Program
- • 12.9 Cycle 21 Calibration Program
- • 12.10 Cycle 22 Calibration Program
- • 12.11 Cycle 23 Calibration Program
- • 12.12 Cycle 24 Calibration Program
- • 12.13 Cycle 25 Calibration Program
- • 12.14 Cycle 26 Calibration Program
- • 12.15 Cycle 27 Calibration Program
- • 12.16 Cycle 28 Calibration Program
- • 12.17 Cycle 29 Calibration Program
- Chapter 13: Spectroscopic Reference Material
- • Glossary