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- Interstellar Medium Absorption Profile Spectrograph
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- Entrance aperture
- Multi-grid mechanical collimator with tandem square aperture arrays to
provide field restriction
- Area: 250
cm2
- Field of view:
1° FWHM
- Mechanical obscuration: 26%
- Losses from diffraction and scattering: 16%
- Primary beam throughput: 62%
- Optical elements
- Echelle grating
- Ruled area 200✕400
mm
- Groove freq
79 mm-1
- Blaze angle
63.4°
- Meas. Efficiency @ 1040Å 24%
- Angles of α = β
= 63.4°±
0.15°, ±0.30° and diffraction (4 settings)
- Off-plane angle: γ = 3.5°
- Cross-disperser grating
- Ruled area:
190✕143 mm
- Groove freq: 171
mm-1
- Blaze angle: 0.5°
(8 ½ partitions)
- Width of each partition 17 mm
- Theoretical resolution 0.34Å = 11μm at focus of each partition
- Worst efficiency away from 79% blaze maximum
- Figure
Off-axis paraboloid
- Focal length 1800
mm
- Chief ray decenter distance 130 mm
- Distance from echelle grating
1200 mm
- Measured efficienty @ 1040Å 25% (incl. coating and
blaze efficiencies
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- Detector
- Photocathode
- Material
KBr
- Quantum efficiencies
83% @ 950Å
-
77% @ 1000Å
-
74% @ 1150Å
- Permanent Magnet Focus Assembly
- Field strength 132
gauss
- Angle between B and E 20°
- Field uniformity 2 gauss
- Electrostatic assembly
- Operating voltage 18.5 kV
- CCD (RCA type SID-502)
- Pixel format 320 ✕
256
- Active area
9.6 mm ✕ 7.7mm
- Charge well dimensions 30μm
✕ 30μm
- Charge well capacity
8.5 ✕ 105 e-
- Amplifier output 1.5μV/e-
- Secondary electron yield for
2500 e- for 18.5 kV
- Lateral spread of secondary
8 – 12 μm electrons (distance between 1/e points)
- Output signal characteristics
- Frame rate
15 Hz
- Pixel dwell time 0.60 μs
- Frame transfer time: A→B register 1.78ms
- rms noise in each pixel 75e-
- Dark current:
3000 e- @20° C
- ( varies by ~30% over the image format)
- Image Layout
- Angles in the sky
- CCD field of view
18’20” ✕ 14’40”
- Image scale 115”
mm-1
- CCD pixel
3.45”
- Lowest echelle order 197
- Order separation 178 μm
- Central λ
1150 Å
- Free spectral range
35.5 mm = 5.5 Å
- Highest useful echelle order 238
- Order separation 122 μm
- Central λ
950 Å
- Free spectral range
29.0 mm = 3.7 Å
- Echelle angle settings
- Number
4
- Overlap of adjacent settings 0.42 mm
- Sample characteristics
- Mean dispersion: (λ/1000Å)✕
0.139Å mm-1
- Sample size along orders 30 μm
- Sample size ┴ to orders 30 μm
- Instrumental profile 60
– 90 μm FWHM (Δλ
≥ λ/2.3 ✕ 105)
- Broad band star images for guidance corrections (sounding rocket
flights only)
- Location 0.78 mm (90”)
from short λ edge
- Brightness ~ 50
events per 1/15 s frame
- λ range
1250 – 1500 Å
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- Windowless, Electron-bombarded Intensified CCD Image Sensor
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- 3 Sounding Rocket Flights: October 1984, April 1985 and September 1988
- 2 Shuttle-launched ORFEUS-SPAS missions: STS-51 Sept. 12-22, 1993 and
STS-80 Nov. 20 – Dec. 4, 1996
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- Spectrum of B Sco extracted from data recorded on a 5-minute
sounding rocket flight in April 1985.
(Results published in Jenkins, Lees, van Dishoeck & Wilcots
1989, ApJ, 343, 785.) Resolving
power 8/Δ8 ≥ 1.3×105 (2.3 km s-1)
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- Scientific articles:
- E. B. Jenkins, J. F. Lees, E. F. van Dishoeck, and E. M. Wilcots (1989):
"Velocities and Rotational Excitation of Interstellar H2
toward π Scorpii“ Astrophysical Journal, 343, pp. 785-810.
- C. L. Joseph and E. B. Jenkins (1991): "UV interstellar lines in
the spectrum of π Scorpii recorded at 2 kilometers per second
resolution“ Astrophysical Journal, 368, pp. 201-214.
- F. Bertoldi and E. B. Jenkins (1992): "Dense Clumps of ionized gas
near π Scorpii, as revealed by the fine-structure excitation of N
II" Astrophysical Journal, 388, pp. 495-512.
- E. B. Jenkins and A. Peimbert (1997): "Molecular hydrogen in the
direction of ζ Ori A" Astrophysical Journal, 477, pp. 265-280.
- U. J. Sofia and E. B. Jenkins (1998): "Interstellar Medium
Absorption Profile Spectrograph Observations of Interstellar Neutral
Argon and the Implications for Partially Ionized Gas" Astrophysical
Journal, 499, pp. 951-965.
- E. B. Jenkins, U. J. Sofia, and G. Sonneborn (1998): "Observations
of interstellar O VI absorption at 3 km/s resolution" in The Hot
Universe, K. Koyama, S. Kitamoto,
and M. Itoh, (Kluwer, Dordrecht)
271-272.
- S. P. Sarlin (1998): “Ultraviolet studies on interstellar molecular
hydrogen.” Ph.D. Dissertation,
University of Colorado, Boulder. 186 p.
- E. B. Jenkins, T. M. Tripp, P. R.
Wozniak, U. J. Sofia, and G. Sonneborn (1999): "Spatial Variability
in the Ratio of Interstellar Atomic Deuterium to Hydrogen. I.
Observations toward δ Orionis by the Interstellar Medium Absorption
Profile Spectrograph" Astrophysical Journal, 520, pp. 182-195.
- G. Sonneborn, E. B. Jenkins, T. Tripp, P. Wozniak, R. Ferlet, A. Vidal-
Madjar, and U. J. Sofia (2000): "Spatial variations in the atomic
D/H ratio in the ISM" in The Light elements and their Evolution, L.
da Silva, M. Spite, and R. de Medeiros,
(Astr. Soc. Pacific, San Francisco) 242-243.
- E. B. Jenkins, P. R. Wozniak, U. J. Sofia, G. Sonneborn, and T. M. Tripp
(2000): "The Properties of Molecular Hydrogen toward the Orion Belt
Stars from Observations by the Interstellar Medium Absorption Profile
Spectrograph“ Astrophysical Journal, 538, pp. 275-288.
- G. Sonneborn, T. M. Tripp, R. Ferlet, E. B. Jenkins, U. J. Sofia, A.
Vidal-Madjar, and P. R. Wozniak (2000): "Spatial Variability in the
Ratio of Interstellar Atomic Deuterium to Hydrogen. II. Observations
toward γ2 Velorum
and ζ Puppis by the Interstellar Medium Absorption Profile
Spectrograph" Astrophysical Journal, 545, pp. 277-289.
- E. B. Jenkins, C. Gry, and O. Dupin (2000): "Electron densities,
temperatures and ionization rates in two interstellar clouds in front of
β Canis Majoris, as revealed by UV absorption lines observed with
IMAPS“ Astronomy and Astrophysics, 354, pp. 253-260.
- C. Gry and E. B. Jenkins (2001): "Local clouds: Ionization,
temperatures, electron densities and interfaces, from GHRS and IMAPS
spectra of ε Canis Majoris" Astronomy and Astrophysics, 367,
pp. 617-628.
- D. E. Welty, E. B. Jenkins, J. C. Raymond, C. Mallouris, and D. G. York
(2002): "Intermediate- and high-velocity ionized gas toward ζ
Orionis“ Astrophysical Journal, 579, pp. 304-326.
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- Technical or Instrumental articles:
- E. B. Jenkins, C. L. Joseph, D. Long, P. M. Zucchino, G. R. Carruthers,
M. Bottema, and W. A. Delamere (1988): "IMAPS: a high-resolution,
echelle spectrograph to record far-ultraviolet spectra of stars from
sounding rockets“ in Ultraviolet Technology II R. E. Huffman, (The International Society for Optical
Engineering, Bellingham) 213-229.
- E. B. Jenkins, C. L. Joseph, M. A. Reale, P. Zucchino, and T. B.
Williams (1990): "Use of a high-density digital tape drive to
improve complex spectroscopic data acquisition" Spectroscopy, 5,
pp. 37-40.
- M. Reale (1990): “Serial transmission of digitized video over an RF link
using the Advanced Micro Devices TAXI chipset” in Advanced Devices
Article Reprints, 33‑.
- E. B. Jenkins, M. A. Reale, P. M. Zucchino, and U. J. Sofia (1996): "High
resolution spectroscopy in the far uv: Observations of the interstellar
medium by IMAPS on ORFEUS-SPAS" Astrophysics and Space Science,
239, pp. 315-360.
- E. B. Jenkins (1993): "The IMAPS instrument: A new horizon for
recording the real shapes of interstellar absorption lines in the far
UV" in UV and X-ray Spectroscopy of Astrophysical and Laboratory
Plasmas, E. H. Silver and S. M. Kahn,
(Cambridge U. Press, Cambridge) 254-269.
- E. B. Jenkins (1995): "IMAPS Observations of Interstellar
Absorption Lines between 950 and 1150 A at 2 km/s Resolution" in Laboratory
and Astronomical High Resolution Spectra, A. J. Sauval, R. Blomme, and N.
Grevesse, (Astronomical Society of the Pacific, San Francisco) 453-458.
- E. B. Jenkins, M. A. Reale, and P. M. Zucchino (1999): “Development of a
photon‑counting capability for the electron‑bombarded
far‑UV image sensor” in Ultraviolet
and X‑Ray Detection, Spectroscopy, and Polarimetry III, S.
Fineschi, B. E. Woodgate, and R. A. Kimble, (SPIE (Intl. Soc. for Optical Eng.),
Bellingham) 226‑233.
- Analysis Methodology inspired by IMAPS results:
- E. B. Jenkins (1996): "A procedure for correcting the apparent
optical depths of moderately saturated interstellar absorption
lines" Astrophysical Journal, 471, pp. 292-301
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