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Appendix A:
Orbit Calculation Examples


In this appendix . . .
 

Chapter 6 described the issues involved in the construction of an observing program, and in the calculation of the total orbit request for a Phase I proposal. As an illustration, this Appendix contains some specific, simple example orbit calculations for each of the SIs offered in Cycle 12.

A.1 ACS

Suppose that you wish to use the ACS to observe a target at a declination of +35 degrees, so that there are 54 minutes of visibility time per orbit (see Table 6.1). Your desired exposures are listed in Table A.1, and the associated overheads are listed in Table A.2. In Table A.3 you can see how the observations fit into a total of 2 orbits.

Table A.1: ACS Example: Planned Exposures
Config
Mode
Spectral
Element
Number of Exp
Time per Exp [m]
Notes
ACS/WFC
IMAGING
F606W
4
8.5
Pattern (see Section 5.4) with an offset of 25" between positions
ACS/HRC
IMAGING
F814W
2
6
CR-SPLIT
ACS/HRC
IMAGING
F606W
2
6
CR-SPLIT
ACS/HRC
IMAGING
F435W
2
7
CR-SPLIT
Table A.2: ACS Example: Incurred Overheads
Overhead
Overhead Time [m]
Notes
see
Table
Guide star acquisition
6
First orbit in new visit
6.2
Guide star re-acquisition
5
Per orbit after first orbit
6.2
WFC exposure (first)
4
First exposure in a series of identical exposures
6.4
WFC exposure (not first)
2.5
Per exposure after the first exposure in a series
6.4
HRC exposure (first)
2.5
First exposure in a series of identical exposures
6.4
HRC exposure (not first)
1
Per exposure after the first exposure in a series
6.4
SAM of 25"
0.5
Small Angle Maneuver between positions in the pattern
Table A.3: ACS Example: Orbit Planning
Activity
Duration [m]
Elapsed Time [m]
Orbit 1
 
 
Guide star acquisition
6
6
WFC/F606W Exp Time
4x8.5
40
WFC/F606W Overhead
4+(3x2.5)+(3x0.5)
53
Unused time
1
54
Orbit 2
 
 
Guide star re-acquisition
5
5
HRC/F814W Exp Time
2x6
17
HRC/F814W Overhead
2.5+1
20.5
HRC/F606W Exp Time
2x6
32.5
HRC/F606W Overhead
2.5+1
36
HRC/F435W Exp Time
2x7
50
HRC/F435W Overhead
2.5+1
53.5
Unused time
0.5
54

A.2 FGS

Suppose that you wish to use the FGS to observe a binary star named Binary01, as well as five reference stars ref1,......,ref5. All stars are in the same FGS field of view, and can therefore be observed in one and the same visit (see Section 6.2.3). Stars ref4 and ref5 have magnitude V=14.6, and all the other targets have 13.0<V<14.0. The targets have a declination of +42 degrees, so that there are 54 minutes of visibility time per orbit (see Table 6.1). To enable the removal of drift and jitter in the post observation analysis of the data, the binary is observed in POS mode three times and the reference stars are each observed twice. Your desired exposures are listed in Table A.4, and the associated overheads are listed in Table A.5. In Table A.6 you can see how this fits into a total of 1 orbit.

Table A.4: (Continued)FGS Example: Planned Exposures
Config
Mode
Spectral Element
Number of Exp
Time per Exp [m]
Notes
FGS
POS
F583W
8
0.2
2 exposures of target Binary01, and 2 exposures for each of the targets ref1, ref2 and ref3
FGS
POS
F583W
4
0.7
2 exposures for each of the targets ref4 and ref5
FGS
TRANS
F583W
1
13.3
20 scans of 40 sec each (see Table 6.8) for Binary01
Table A.5: FGS Example: Incurred Overheads
Overhead
Overhead
Time [m]
Notes
see Table
Guide star acquisition
6
First orbit in new visit
6.2
POS
1
per exposure, V<14
6.6
POS
2
per exposure, 14<V<15
6.6
TRANS
1
per target
6.6
TRANS
0.2
per scan
6.6
Instrument Setup
4
once every orbit
6.7
Instrument Shutdown
3
once every orbit
6.7
Table A.6: FGS Example: Orbit Planning
Activity
Duration [m]
Elapsed Time [m]
Orbit 1
 
 
Guide star acquisition
6
6
Instrument Setup
4
10
Binary01/POS mode Exp Time
0.2
10.2
Binary01/POS mode Overhead
1
11.2
ref1/POS mode Exp Time
0.2
11.4
ref1/POS mode Overhead
1
12.4
ref2/POS mode Exp Time
0.2
12.6
ref2/POS mode Overhead
1
13.6
ref3/POS mode Exp Time
0.2
13.8
ref3/POS mode Overhead
1
14.8
ref4/POS mode Exp Time
0.7
15.5
ref4/POS mode Overhead
2
17.5
ref5/POS mode Exp Time
0.7
18.2
ref5/POS mode Overhead
2
20.2
Binary01/POS mode Exp Time
0.2
20.4
Binary01/POS mode Overhead
1
21.4
ref1/POS mode Exp Time
0.2
21.6
ref1/POS mode Overhead
1
22.6
ref2/POS mode Exp Time
0.2
22.8
ref2/POS mode Overhead
1
23.8
ref3/POS mode Exp Time
0.2
24.0
ref3/POS mode Overhead
1
25.0
ref4/POS mode Exp Time
0.7
25.7
ref4/POS mode Overhead
2
27.7
ref5/POS mode Exp Time
0.7
28.4
ref5/POS mode Overhead
2
30.4
Binary01/POS mode Exp Time
0.2
30.6
Binary01/POS mode Overhead
1
31.6
Binary01/TRANS mode Exp Time
13.2
44.8
Binary01/TRANS mode Overhead
1+(20x0.2)
49.8
Instrument Shutdown
3
52.8
Unused
1.2
54.0

A.3 NICMOS

Suppose that you wish to use the NICMOS to observe a target at a declination of -50 degrees, so that there are 56 minutes of visibility time per orbit (see Table 6.1). Your desired exposures are listed in Table A.7, and the associated overheads are listed in Table A.8. In Table A.9 you can see how the observations fit into a total of 1 orbit.

Table A.7: NICMOS Example: Planned Exposures
Config
Mode
Spectral
Element
Number of Exp
Time per Exp [m]
Notes
NIC2
IMAGING
F110W
4
2.1
Pattern (see Section 5.4) of MULTIACCUM exposures with an offset of 1" between dither positions
NIC2
IMAGING
F160W
4
4
Pattern (see Section 5.4) of MULTIACCUM exposures with an offset of 1" between dither positions
 
NIC2
IMAGING
F222M
4
4
Pattern (see Section 5.4) of MULTIACCUM exposures with an offset of 1" between dither positions
Table A.8: NICMOS Example: Incurred Overheads
Overhead
Overhead Time [m]
Notes
see Table
Guide star acquisition
6
First orbit in new visit
6.2
MULTIACCUM exposure
0.07
 
6.9
Instrument Setup
0.3
Beginning of each orbit
Filter change
0.3
 
SAM of 1"
0.33
Small Angle Maneuver between positions in the pattern
Table A.9: NICMOS Example: Orbit Planning
Activity
Duration [m]
Elapsed Time [m]
Orbit 1
 
 
Guide star acquisition
6
6
Instrument Setup
0.3
6.3
F110W Exp Time
2.1
8.4
F160W Exp Time
4
12.4
F222M Exp Time
4
16.4
Overhead
(3x0.07) + (2x0.3) + (1x0.33)
17.4
F110W Exp Time
2.1
19.5
F160W Exp Time
4
23.5
F222M Exp Time
4
27.5
Overhead
(3x0.07) + (3x0.3) + (1x0.33)
28.9
F110W Exp Time
2.1
31.0
F160W Exp Time
4
35.0
F222M Exp Time
4
39.0
Overhead
(3x0.07) + (3x0.3) + (1x0.33)
40.4
F110W Exp Time
2.1
42.5
F160W Exp Time
4
46.5
F222M Exp Time
4
50.5
Overhead
(3x0.07) + (3x0.3) + (1x0.33)
51.9
Unused
4.1
56

A.4 STIS

Suppose that you wish to use the STIS to observe a target at a declination of +15 degrees, so that there are 52 minutes of visibility time per orbit (see Table 6.1). Your desired exposures are listed in Table A.10, and the associated overheads are listed in Table A.11. In Table A.12 you can see how this fits into a total of 2 orbits.

Table A.10: STIS Example: Planned Exposures
Config
Mode
Spectral
Element
Number of Exp
Time per Exp [m]
Notes
STIS/CCD
ACQ
 
 
 
target acquisition
STIS/CCD
ACQ/PEAK
 
 
 
peakup acquisition (necessary because of use of 0.1" wide slit for subsequent spectra)
STIS/CCD
IMAGING
F28X50OII
2
2
 
STIS/NUV
IMAGING
F25QTZ
1
19
 
STIS/NUV
SPECTROSCOPIC
G230L
1
13
with 52X0.1 slit
STIS/FUV
SPECTROSCOPIC
G140L
1
17
with 52X0.1 slit
Table A.11: STIS Example: Incurred Overheads
Overhead
Overhead Time [m]
Notes
see Table
Guide star acquisition
6
first orbit in new visit
6.2
Guide star re-acquisition
5
per orbit after first orbit
6.2
ACQ
6
target acquisition
6.3
ACQ/PEAK
6
peakup target acquisition
6.3
CCD imaging
5
but only 1m if no change from previous exposure
MAMA imaging
5
but only 1m if no change from previous exposure
MAMA spectroscopy
8
but only 1m if no change from previous exposure
Table A.12: STIS Example: Orbit Planning
Activity
Duration [m]
Elapsed Time [m]
Orbit 1
 
 
Guide star acquisition
6
6
ACQ
6
12
ACQ/PEAK
6
18
F28X50OII Exp Time
2x2
22
F28X50OII Overhead
5+1
28
F25QTZ Exp Time
19
47
F25QTZ Overhead
5
52
Orbit 2
 
 
Guide star re-acquisition
5
5
G230L Exp Time
13
18
G230L Overhead
8
26
G140L Exp Time
17
43
G140L Overhead
8
51
Unused
1
52

A.5 WFPC2

Suppose that you wish to use the WFPC2 to observe a target at a declination of -45 degrees, so that there are 55 minutes of visibility time per orbit (see Table 6.1). Your desired exposures are listed in Table A.13 and the associated overheads are listed in Table A.14. In Table A.15 you can see how the observations fit into a total of 3 orbits.

Table A.13: WFPC2 Example: Planned Exposures
Config
Mode
Spectral
Element
Num of Exp
Time per Exp [m]
Notes
WFPC2
IMAGING
F814W
1
40
CR-SPLIT
WFPC2
IMAGING
F450W
1
43
CR-SPLIT
WFPC2
IMAGING
F555W
4
9
Pattern (see Section 5.4 ) with an offset of 1" between positions
Table A.14: WFPC2 Example: Incurred Overheads
Overhead
Overhead Time [m]
Notes
see Table
Guide star acquisition
6
first orbit in new visit
6.2
Guide star re-acquisition
5
per orbit after first orbit
6.2
Exposure (CR-SPLIT)
5
per exposure (CR-SPLIT is default for >600s)
Exposure (no CR-SPLIT)
3
per exposure (no CR-SPLIT is default for <=600s)
Efficiency
1
per orbit
SAM of 1"
0.33
Small Angle Maneuver between positions in the pattern
Table A.15: WFPC2 Example: Orbit Planning
Activity
Duration [m]
Elapsed Time [m]
Orbit 1
 
 
Guide star acquisition
6
6
F814W Exp Time
40
46
F814W Overhead
5
51
Efficiency Overhead
1
52
Unused
3
55
Orbit 2
 
 
Guide star re-acquisition
5
5
F450W Exp Time
43
48
F450W Overhead
5
53
Efficiency Overhead
1
54
Unused
1
55
Orbit 3
 
 
Guide star re-acquisition
5
5
F555W Exp Time
4x9
41
F555W Overhead
(4x3)+(3x0.33)
54
Efficiency Overhead
1
55

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