Cosmic Origins Spectrograph Instrument Handbook for Cycle 17

9.6 Examples of Orbit Estimates

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9.6.1 FUV Acquisition plus FUV TIME-TAG

In this example we start with an FUV ACQ/SEARCH followed by an ACQ/PEAKXD, then ACQ/PEAKD target acquisition, then add an FUV TIME-TAG exposure with G140L and SEGMENT=A.

Table 9.5: Overhead Values for FUV Acquisition with FUV TIME-TAG.

Action	Time required	Comment
Initial guide star acquisition	6 min	Required at start of a new visit
FUV ACQ/SEARCH, G130M at 1309 Å, 3 × 3 pattern, 15 sec exp.	9×(20+15) = 315 sec = 5.3 min	COS starts from G130M home on OSM1 so no initial move; 9 ACQ/SEARCH sub-exposures, so overhead includes 9 slews (20 sec each) plus 9 exposures (15 sec each)
FUV ACQ/PEAKXD, G130M at 1309 Å, 20 sec exp.	80 + 20 sec = 100 sec = 1.7min	No OSM1 movement; generic PEAKXD overhead; exp time
FUV ACQ/PEAKD, G130M at 1309 Å, 5 steps, 25 sec exp.	5×(20+25) = 225 sec = 3.8 min	No OSM1 move; five slews (20 sec each) plus 5 exp (25 sec each)
FUV G140L at 1235 Å, TIME-TAG, FLASH=YES, FP-POS=3, SEGMENT=A, 1500 sec exp.	71 + 164 + 330 + 110 + 1500 = 2175 sec = 36.3 min	Generic FUV TIME-TAG setup; OSM1 grating change (164); no central wavelength change; no FP-POS change; SEGMENT reconfiguration change; TIME-TAG memory readout; exp time
Total science time	36.3 min
Total time used in orbit	53.1 min

9.6.2 NUV TIME-TAG

In this example we start with an NUV ACQ/IMAGE target acquisition, then add two NUV TIME-TAG exposures with the same grating, but different central wavelengths, both utilizing default FP-POS and FLASH=YES.

Table 9.6: Overhead Values for NUV TIME-TAG.

Action	Time required	Comment
Initial guide star acquisition	6 min	Required at start of a new visit
NUV ACQ/IMAGE with 2 sec exposure time	7 min + 4 sec	ACQ/IMAGE is first exposure in visit, thus we include OSM1 change to NCM1 and OSM2 move to MIRRORA
NUV G185M at 1850 Å, TIME-TAG, FLASH=YES, FP-POS=3, 1200 sec exp.	36 + 174 + 110 + 1200 = 1520 sec = 25.3 min	Generic NUV TIME-TAG setup; change from MIRRORA to G185M [174]; no central wavelength change (default value); no FP-POS change (3=default); no aperture change from PSA; TIME-TAG memory readout; exp time
NUV G185M at 1812 Å, TIME-TAG, FLASH=YES, FP-POS=3, 600 sec exp.	36 + 75 + 110 + 600 = 785 sec = 13.1 min	Only change central wavelength, so generic NUV TIME-TAG exposure setup; no grating change; central wavelength change [75 sec]; no FP-POS change; TIME-TAG memory readout; exp time
Total science time1	38.4 min
Total time used in orbit	51.4 min

1The indicated science time has been chosen to be less than the orbit visibility period less the various overheads.

9.6.3 NUV plus FUV TIME-TAG

In this example we start with an NUV ACQ/SEARCH followed by an ACQ/IMAGE target acquisition, then add an NUV TIME-TAG exposure followed by a switch to the FUV channel and an FUV TIME-TAG exposure.

Table 9.7: Overhead Values for NUV ACCUM with FUV TIME-TAG.

Action	Time required	Comment
Initial guide star acquisition	6 min	Required at start of a new visit
NUV ACQ/SEARCH, MIRRORA, 3 × 3 pattern, 10 sec exp.	116 + 169 + 9×(20+10) = 555 sec = 9.3 min	COS starts at G130M on OSM1, so move to NCM1 requires 116 sec; OSM2 home position is G185M, so move to MIRRORA takes 169 sec; 9 ACQ/SEARCH sub-exposures, so overhead includes 9 slews (20 sec each) plus 9 exposures (10 sec each)
NUV ACQ/IMAGE with 10 sec exposure time	2 min + 2×10 sec = 140 sec = 2.3 min	No OSM2 movement; so overhead includes only ACQ/IMAGE setup and twice exp. time
NUV G225M at 2250 Å, TIME-TAG, FLASH=YES, FP-POS=3, 1200 sec exp.	36 + 105 + 110 + 1200 = 1451 sec = 24.2 min	Generic NUV TIME-TAG setup; change from MIRRORA to G225 [105]; no central wavelength change (default value); no FP-POS change (3=default); no aperture change from PSA; TIME-TAG memory readout; exp time
FUV G130M at 1309 Å, TIME-TAG, FLASH=YES, FP-POS=3, 600 sec exp.	71 + 109 + 110 + 600 = 840 sec = 14.9 min	Switch from FUV to NUV adds no overhead (OSM2 not moved); generic FUV TIME-TAG setup; OSM1 move from NCM1 to G130M [109]; no central wavelength change; no FP-POS change; no SEGMENT change; TIME-TAG memory readout; exp time
Total science time	39.1 min
Total time used in orbit	56.7 min

9.6.4 FUV TIME-TAG with BOA and FLASH=NO

In this example we start with an NUV ACQ/IMAGE followed by a switch to the FUV channel and an FUV TIME-TAG science exposure with G160M, the BOA, and, as required with the BOA, FLASH=NO. The science exposure will be followed automatically by a 10-second wavecal (see Section 5.7.3). The next orbit starts with a longer science exposure using the same set-up as for the first orbit. Because more than 40 minutes will have elapsed since the first wavecal, another wavecal will be inserted automatically following this science exposure.

Table 9.8: Overhead Values for FUV TIME-TAG Using the BOA and FLASH=NO.

Action	Time required	Comment
Initial guide star acquisition	6 min	Required at start of a new visit
NUV ACQ/IMAGE, 2 sec exp.	7 min + 4 sec	ACQ/IMAGE is first exposure in visit, so overhead includes OSM1 change to NCM1; OSM2 move to MIRRORA
FUV G160M at 1600 Å, TIME-TAG, BOA, FLASH=NO, FP-POS=1, 1800 sec exp.	71 + 154 + 68 + 8 + 110 + 1800 sec = 2211 sec = 36.8 min	Generic FUV TIME-TAG setup; NUV to FUV adds no overhead; change from NCM1 to G160M [154]; no central wavelength change (default value); non-preferred direction FP-POS change [70 sec] (3=default to 1); aperture change from PSA to BOA; no SEGMENT change; TIME-TAG memory readout; exp time
FUV G160M at 1600 Å, TIME-TAG, AUTO WAVECAL, WCA, FP-POS=1, 10 sec exp.	71 + 10 + 110 = 191 sec = 3.2 min	AUTO WAVECAL to be inserted as FLASH=YES not allowed with BOA; generic FUV TIME-TAG setup; no OSM1 move, no central wavelength change; no FP-POS change; aperture change from BOA to WCA [10 sec]; no SEGMENT change; TIME-TAG memory readout; exp time
end of orbit 1; total science time = 40.0 min.; total time used = 53.1 min.
Guide star re-acquisition	5 min	required at start of additional orbit
FUV G160M at 1600 Å, TIME-TAG, BOA, FLASH=NO, FP-POS=1, 2400 sec exp.	71 + 10 + 110 + 2400 = 2591 sec = 43.2 min	Generic FUV TIME-TAG setup; continue at same OSM1 position, same central wavelength and FP-POS; aperture change to BOA [10 sec]; no SEGMENT change; TIME-TAG memory readout; exp time
FUV G160M at 1600 Å, TIME-TAG, AUTO WAVECAL, WCA, FP-POS=1, 10 sec exp.	71 + 10 + 110 = 191 sec = 3.2 min	Another AUTO WAVECAL required as more than 40 min have elapsed since last one; again generic FUV TIME-TAG exposure setup; no grating change; no central wavelength change; no FP-POS change; aperture change from PSA to BOA [8 sec]; no SEGMENT change; TIME-TAG memory readout; exp time
Total science time (orbit 2)	45.4 min
Total time used in orbit 2	50.4 min

9.6.5 FP-POS=AUTO with FUV TIME-TAG and FLASH=YES

In this example we start with an NUV ACQ/IMAGE target acquisition followed by a switch to the FUV channel for an FP-POS=AUTO sequence (using a single exposure entry from which four individual exposures are automatically generated; that is, one exposure at each FP-POS wavelength dither position). In this example we will again use TIME-TAG, FLASH=YES, and G130M, but we will also use central wavelength 1327 rather than the default value of 1309. For FP-POS=AUTO sequences the observer specifies the total duration of the four individual exposures to be obtained in the sequence.

First an NUV ACQ/IMAGE will be performed. Next OSM1 is moved to put G130M in place at the standard default central wavelength position (_c = 1309 Å). Next, OSM1 is moved to select central wavelength 1327 at default FP-POS=3. Following this, the FP-POS=AUTO sequence will be executed. Since in an FP-POS=AUTO sequence the individual exposures will be executed in the order FP-POS=1, 2, 3, and 4, a non-preferred direction (backward) movement from position 3 to position 1 is performed first. After the position 1 exposure, a forward direction movement is made to position 2 and so on for positions 3 and 4. In the example provided, the total exposure time will not fit into a single orbit, so, as in the previous example, some exposures must be performed in a second orbit. As the second orbit is not completely filled, the observer would typically add additional exposures (not shown here) to fill that orbit.

Table 9.9: Overhead Values for FP-POS=AUTO with FUV TIME-TAG and FLASH=YES.

Action	Time required	Comment
Initial guide star acquisition	6 min	Required at start of a new visit
NUV ACQ/IMAGE, 10 sec exp., aperture = PSA	7 min + 20 sec = 7.3 min.	ACQ/IMAGE is first exposure in visit, so overhead includes OSM1 change to NCM1; OSM2 move to MIRRORA; add twice exposure time
FUV G130M at 1327 Å, TIME-TAG, BOA, FLASH=YES, FP-POS=AUTO, 3600 sec exp.	109 + 72 sec = 181 sec = 3 min	Move OSM1 from NCM1 to G130M (109 sec.); change G130M from default setting of 1309 to desired 1327 (72 sec.); default FP-POS=3
FP-POS=1 exposure	71 + 70 + 110 +900 = 1151 sec = 19.2 min	First exposure of FP-POS sequence: generic TIME-TAG set-up (71 sec.); move to position 1 (70 sec.); TIME-TAG memory read-out (110 sec.); exposure time = 3600/4 = 900 sec.
FP-POS=2 exposure	71 + 3 + 110 +900 = 1151 sec = 18.1 min	First exposure of FP-POS sequence: generic TIME-TAG set-up (71 sec.); move to position 1 (70 sec.); TIME-TAG memory read-out (110 sec.); exposure time = 3600/4 = 900 sec.
Total science time in orbit 1	40.3 min
Total time used in orbit 1	53.6 min
Guide star re-acquisition	5 min	required at start of additional orbit
FP-POS=3 exposure	71 + 3 + 110 +900 = 1151 sec = 18.1 min	As for FP-POS=2
FP-POS=4 exposure	71 + 3 + 110 +900 = 1151 sec = 18.1 min	As for FP-POS=2
Total science time in orbit 2	36.2 min
Total time used in orbit 2	42.2 min