9.4 Acquisition Overheads
The various target-acquisition procedures are described in detail in Chapter 8. The approximate total exposure plus associated overheads are given for each procedure below:
ACQ/SEARCH:
Multiply the exposure time by the number of dwell points (SCAN-SIZE2
); add times to move OSM1, OSM2, and the aperture, if necessary; add the overhead below for the correct SCAN-SIZE
; and add 37 s for readout to estimate the total ACQ/SEARCH
time.
SCAN-SIZE | Overhead Time(s) |
---|---|
2 | 170 |
3 | 306 |
4 | 535 |
5 | 790 |
Note that these overheads assume the standard (default) STEP-SIZE
of 1.767". Overheads are slightly shorter for smaller STEP-SIZE
s.
ACQ/IMAGE
: Multiply the exposure time by 2 (since images are obtained before and after centering); add times to move OSM1, OSM2, and the aperture, if necessary; add 120 s for setup; and add 56 s for readout to estimate the total ACQ/IMAGE
time.
ACQ/PEAKXD
: For NUV, start with the exposure time; add times to move OSM1, OSM2, and the aperture, if necessary; add 86 s for setup; and add 37 s for readout to estimate the total ACQ/PEAKXD
time. For FUV, use the timing outlined below for ACQ/PEAKD
. The default FUV ACQ/PEAKXD
configuration uses NUM-POS=3
and STEP-SIZE=1.3
.
ACQ/PEAKD
: Multiply the exposure time by the number of dwell points (NUM-POS
); add times to move OSM1, OSM2, and the aperture, if necessary; add the overhead below for the correct NUM-POS
; and add 37 s for readout to estimate the total ACQ/PEAKD
time. The numbers below assume the default STEP-SIZE
for each NUM-POS
as given in Table 8.3.
NUM-POS | Overhead Time(s) |
---|---|
3 | 115 |
5 | 168 |
7 | 219 |
9 | 274 |
Note that the above estimates assume that all TA steps were taken with the same grating and cenwave or mirror configuration. If a change of configuration is used, add the appropriate overheads from Table 9.3 and Table 9.4.
-
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