Effect of the Shuttle contaminant environment on a sensitive infrared
telescope

J. P. Simpson; F. C. Witteborn

doi:10.1364/AO.16.002051

Applied Optics
Vol. 16,
Issue 8,
pp. 2051-2073
(1977)
•https://doi.org/10.1364/AO.16.002051

Effect of the Shuttle contaminant environment on a sensitive infrared telescope

J. P. Simpson and F. C. Witteborn

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J. P. Simpson and F. C. Witteborn, "Effect of the Shuttle contaminant environment on a sensitive infrared telescope," Appl. Opt. 16, 2051-2073 (1977)

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Abstract

A sensitive ir telescope on the Space Shuttle Orbiter will be limited in its performance by fluctuations in the ir radiation from the natural environment and the contaminant atmosphere. Models of the Orbiter’s contaminant atmosphere were used to predict its spectral radiance from 3 μm to 300 μm. At 350 km, statistical fluctuations in the radiation from a water vapor column density of 10¹² cm⁻² produce a noise equivalent power of about 2 × 10⁻¹⁷ W/Hz^1/2 in a 1 min of arc field of view of a 1-m diameter telescope with a 10-μm spectral bandwidth. This noise is somewhat smaller than the expected contribution from zodiacal light from 5 μm to 30 μm. The column density of all ir emitting molecules can be kept as low as 10¹² cm⁻² only if restrictions on rocket firings and liquid vents are maintained. The relatively low frequency of particle sightings from Skylab, coupled with improvements in Orbiter venting techniques, indicates that sightings of particles 2 μm and larger in radius will not seriously hamper telescope performance provided that liquid vents and rocket firings are properly restricted.

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	SIRTF			CRDG: Contamination Requirements Definition Group

λ (μm)	NEP in 10 μm band 1 arc min FOV	Time variation of background	Angular variation of background	Time variation of background	Angular variation of background	Max. Background intensity
		W	W	W	W	W

	W/Hz^1/2	sec (arc min)² 10 μm	deg 10 μm (arc min)²	sec μm sr m²	deg μm sr m²	μm sr m²
5	1 × 10⁻¹⁷	2 × 10⁻¹⁷	4 × 10⁻¹⁷	5 × 10⁻¹⁷	1 × 10⁻¹⁰	7 × 10⁻⁹
10–30	1 × 10⁻¹⁷	2 × 10⁻¹⁷	4 × 10⁻¹⁷	5 × 10⁻¹¹	1 × 10⁻¹⁰	1 × 10⁻⁸
30–300	1 × 10⁻¹⁶	2 × 10⁻¹⁶	4 × 10⁻¹⁶	5 × 10⁻¹⁰	1 × 10⁻⁹	1 × 10⁻⁷

		Power on detector (W)

		+Z L.O.S.	50° + X L.O.S.	50° + Y L.O.S.
Offgassed H₂O after 24 hr
Position 1	column density (cm⁻²)	8.7(11)	7.0(11)	6.3(11)
Position 1	power on detector (W)	1.8(−14)	2.3(−14)	1.3(−14)
Position 2	column density	4.0(10)	3.6(10)	4.0(10)
Position 2	power on detector	9.0(−16)	9.2(−16)	9.8(−16)
Position 3	column density	3.3(11)	2.2(11)	4.0(10)
Position 3	power on detector	7.5(−15)	7.0(−15)	9.8(−16)
Contribution from cabin leakage	column density	1.3(11)	5.5(11)	1.3(11)
Contribution from cabin leakage	power on detector	1.1(−15)	4.5(−15)	1.1(−15)
Contribution from evaporators for position 1	column density	9.5(11)	1.8(11)	4.2(12)
Contribution from evaporators for position 1	power on detector	1.1(−14)	3.5(−15)	4.1(−14)

		Power on detector (W)

		+ Z L.O.S.	50° + L.O.S.	50° + Y L.O.S.
Offgassed H₂O after 24 hr
Position 1	10–20 μm	5.2(−15)	5.0(−15)	4.9(−15)
	20–30 μm	3.0(−14)	3.1(−14)	2.3(−14)
	30–40 μm	6.5(−14)	6.1(−14)	4.7(−14)
	40–50 μm	5.0(−14)	4.3(−14)	3.6(−14)
Position 2	10–20 μm	1.5(−15)	1.5(−15)	1.5(−15)
	20–30 μm	1.5(−15)	1.5(−15)	1.5(−15)
	30–40 μm	2.0(−15)	2.0(−15)	2.2(−15)
	40–50 μm	1.7(−15)	1.7(−15)	1.8(−15)
Position 3	10–20 μm	1.8(−15)	1.7(−15)	1.5(−15)
	20–30 μm	8.2(−15)	7.3(−15)	1.5(−15)
	30–40 μm	2.0(−14)	1.5(−14)	2.2(−15)
	40–50 μm	1.7(−14)	1.2(−14)	1.8(−15)
Contribution from cabin leakage	10–20 μm	4.8(−16)	1.0(−15)	4.8(−16)
	20–30 μm	2.6(−15)	1.0(−14)	2.6(−15)
	30–40 μm	7.4(−15)	3.1(−14)	7.4(−15)
	40–50 μm	6.4(−15)	2.7(−14)	6.4(−15)
Contribution from evaporators for position 1	10–20 μm	6.0(−15)	5.5(−15)	8.4(−15)
	20–30 μm	1.8(−14)	3.2(−15)	7.0(−14)
	30–40 μm	5.0(−14)	1.0(−14)	2.2(−13)
	40–50 μm	4.4(−14)	8.7(−15)	2.0(−13)

	Initial velocity (cm/sec)
Particle radius(μm)	5	10	30	50
2	0	0	0.0050	0.0097
3	0	0	0.0077	0.0093
5	0	0	0.0097	0.0095
10	0	0	0.0096	0.0079
40	0	0.0094	0.0077	0.0058
160	0.0094	0.0089	0.0058	0.0053
640	0.0089	0.0063	0.0051	0.0053

V₀ (cm/sec)	No. of particles/sec in field of view	Fraction of time a particle is in the field of view	Average time in field of view for each particle (sec)
5	4.4 (−6)	1.3 (−5)	2.9
10	9.2 (−5)	1.3 (−4)	1.4
20	2.4 (−3)	1.6 (−3)	0.7
30	7.5 (−3)	4.2 (−3)	0.6
50	9.3 (−3)	5.9 (−3)	0.6
all velocities	2.6 (−3)	1.6 (−3)	0.6

Image size ÷ F.O.V.	Chopper throw ÷ field of view
	1	2	3	4
1	0.17	0	0	0
2	0.25	0.10	0	0
3	0.40	0.17	0.07	0
4	0.50	0.29	0.125	0.06
6	0.56	0.44	0.30	0.18
8	0.70	0.55	0.42	0.31
16	0.83	0.74	0.65	0.57
32	0.91	0.86	0.81	0.76
64	0.96	0.93	0.90	0.87
128	0.98	0.96	0.95	0.93
256	0.99	0.98	0.97	0.97
500	0.99	0.99	0.99	0.98
1000	0.99	0.99	0.99	0.99

V₀ (m/sec)	r_d (μm)	Image size (min. of arc)
V₀ (m/sec)	r_d (μm)	<1	1–2	2–4	4–8	8–16	16–32	32–64	64–128	128–256	256–1000	>1000
0.05	80										0.747	0.253
0.05	320										0.945	0.055

0.1	20										0.747	0.253
0.1	80										0.945	0.055
0.1	320									0.287	0.691	0.021

0.3	2.1										0.675	0.325
0.3	10										0.900	0.100
0.3	40									0.331	0.626	0.043
0.3	100								0.167	0.471	0.337	0.025
0.3	316							0.288	0.268	0.202	0.234	0.007

1.0	5									0.474	0.493	0.032
1.0	10								0.277	0.405	0.298	0.020
1.0	32							0.353	0.225	0.185	0.230	0.007
1.0	100					0.129	0.343	0.087	0.085	0.137	0.197	0.022
1.0	316				0.356	0.142	0.046	0.046	0.095	0.116	0.184	0.015

3.0	10					0.023	0.440	0.106	0.076	0.137	0.197	0.022
3.0	32				0.321	0.154	0.061	0.064	0.077	0.125	0.184	0.015
3.0	100		0.185	0.230	0.101	0.018	0.035	0.043	0.083	0.117	0.174	0.014
3.0	316	0.415	0.101		0.009	0.026	0.018	0.043	0.083	0.117	0.174	0.014

10.0	10		0.304	0.111	0.101	0.018	0.035	0.043	0.083	0.117	0.174	0.014
10.0	32	0.417	0.101		0.018	0.018	0.018	0.043	0.083	0.117	0.174	0.014
10.0	100	0.516		0.008	0.026		0.018	0.052	0.075	0.117	0.174	0.014
10.0	316	0.516		0.026	0.009	0.009	0.018	0.043	0.075	0.117	0.174	0.014

Radius (μm)	Power (10⁻⁶ ergs/sec)	νEnergy(10⁻⁷ ergs) in 0.114 sec
4.4	0.31	0.35
5.1	0.49	0.56
6.6	0.94	1.07
7.3	1.13	1.29
8.0	1.28	1.46

Radius (μm)	Power (10⁻⁶ ergs/sec)	νEnergy(10⁻⁷ ergs) in 0.114 sec
4.4	0.31	0.35
5.1	0.49	0.56
6.6	0.94	1.07
7.3	1.13	1.29
8.0	1.28	1.46

Abstract

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Tables (8)

Equations (8)

Applied Optics