1. Infrared Instrumentation for Small Telescopes
Klaus W. Hodapp
University of Hawaii,
Institute for Astronomy
Hilo, Hawaii

2. Why Infrared Astronomy ?C
Credit: Keck Observatory

3. Infrared Astronomy: The Good
IR penetrates interstellar dust (Galactic Center, Star Forming Regions)
Even very high redshift objects are visible.
Cool objects (brown dwarfs and young gas planets) are observable.
Surface mineralogy
Seeing is a little better in the NIR
Adaptive Optics does work in the NIR

4. Example: Dynamics of stars around the central black hole Sagitarius A in our Milky Way
Work by:
Andrea Ghetz et al. and
Reinhardt Genzel et al.

5. High-Redshift Objects Remain Visible at Infrared Wavelengths
“drop out” at short
Wavelengths when Lyman absorption gets red-shifted
to that wavelength.

6. Adaptive optics at 8m-class telescopes works very well at near-infrared wavelenghts.
NGC1333 SVS13 with Keck/OSIRIS
Integral Field Spectroscopy
Credit: SEEDS project

7. The chemical composition of rocky surfaces of planetary objects can be studied with broad, multi-spectral imaging, including infrared wavelengths.
Multi-spectral image of the
Moon, obtained by the Galileo
mission shortly after its launch
towards Jupiter.

8. Infrared Astronomy (from the Ground): The Bad
Thermal background above 1.8µm
OH Airglow worst in H band
Atmospheric Transmission is dependent on water vapor and therefore is variable
Diffraction is of same size as seeing for small telescopes

9. OH Airglow is intense in the near-infrared,
before thermal emission rises for λ ≥ 2 µm.
Credit: Gemini Observatory

10. At mid-infrared wavelengths, ground-based observations are severely limited by thermal background radiation.
Ground-based 10 µm observations are as bad as optical observations during the day, with your telescope on fire !
Credit: Absil et al. (2006)

11. Infrared detector arrays in a CCD-like configuration are only suitable for observations λ ≤ 1.8µm.
A Teledyne H2RG detector array installed in a
GL Scientific test cryostat.
Used for a solar instrument.

12. University of Hawaii, IfA
For longer wavelengths, the detector must be shielded from ambient temperature radiation. Cold Lyot-stop optics reduce the exposure to thermal radiation to exactly the radiation coming through the telescope optics.
The IRIS camera optics:
the field lens is CaF2,
the main lens group is BaF2, Schott SF6 and BaF2
the field flattener lens is CaF2
9/22/2013
University of Hawaii, IfA

13. University of Hawaii, IfA
Mechanical Design of the IRIS Camera Cryostat.
The IRIS camera uses most components of the old QUIRC camera, but has new optics, requiring some level of redesign of the cryostat components.
9/22/2013
University of Hawaii, IfA

14. Atmospheric transmission depends on elevation and weather.

15. Infrared Astronomy: The Ugly
Instruments must be cryogenic above 1.8µm
λ > 1.8µm Instruments require cold pupil stop.
Detectors are an order of magnitude more expensive.
Infrared Photometry requires high, dry and stable sites.
In Summary:
The cost of building and operating an infrared instrument is one order of magnitude higher than for similar optical instruments.

16. Experience from Major Observatories:
After ISO, Spitzer, and Herschel, with SOFIA operational and JWST getting ready, ground-based Observatories are reducing their µm capabilities.
Instruments in the 3.0 – 5.5µm range were expensive to build, but get relatively little use.
Best scientific return is in the 1.0 – 2.5µm (NIR) range.
Carefully evaluate the need for K band.
Time-Domain studies are in their infancy.
Adaptive optics is very important.

17. The Present Generation of Infrared Detector Arrays
Teledyne:
HAWAII-2RG
+ ASIC Readout
Signal offsets of each of the 32 amplifiers can be corrected using reference pixels (R).

18. The NEWFIRM Focal Plane
2×2 Raytheon Orion InSb Arrays, Richard Joyce (NOAO)
Raytheon Orion 2Kx2K InSb arrays
NEWFIRM 4K x 4K array; Mike Merrill
NOAO Gemini Data Workshop

19. The ESO VISTA focal plane is populated with 4×4 mosaic
of Raytheon VIRGO detectors (2Kx2K, 2.5µm, HgCdTe).
Credit: ESO

20. SELEX ES of the U.K.
Is primarily a defense company, but is developing some interesting new detector arrays for astronomy at reasonable prices.

21. 1.75 e/pixel sensitivity with APD gain of 33
APD sensor
ROIC ME788
Cutoff wavelength µm Temperature - 40K Integration time – 5.06ms Bandwidth – 5MHz APD gain – 33x
Optics
Filter K short
Pattern contrast – 1.75 e/pixel
Signal processing
Double correlated clamp 16 frames averaged
Data courtesy of ESO