Scientific/Technical Abstract:

FLITECAM is designed to test the SOFIA telescope assembly imaging and infrared background quality. FLITECAM will provide seeing-limited imaging from 1 - 3 µm and diffraction-limited imaging from 3 - 5.5 µm to cover science applications motivated by good atmospheric transmission and low thermal background. FLITECAM will also provide moderate resolution spectroscopy from 1 to 5.5 µm. FLITECAM will operate simultaneously with the Special Class Instrument HIPO (High-speed Imaging Photometer for Occultations) on SOFIA.

FLITECAM Performance Summary:

The instrument sensitivity and resolution summaries are provided to permit estimating feasibility of scientific investigations. The FLITECAM performance summaries show the expected system performance for Full Operational Capability, which may differ from that during commissioning.

FLITECAM Angular Resolution

FLITECAM uses a 1024 x 1024 pixel array with a pixel scale of 0.48" x 0.48" projected on the sky providing a roughly 8' diameter field of view (FOV). High-speed imaging can be performed at ~12 full frames per second. The maximum readout of 30 kHz is obtained using the 4" x 8"

Shown below is the FLITECAM angular resolution (FWHM, arc-seconds) versus wavelength for nominal operating conditions, including in-flight image quality.

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FLITECAM Spectral Passbands

Wavelength range: 1 - 5.5 µm. FLITECAM provides seeing-limited imaging from 1 - 3 µm and diffraction-limited imaging from 3 - 5.5 µm. It also provides moderate resolution grism spectroscopic capabilities from 1 to 5.5 µm.

Broadband imaging filters are available in the standard J, H, K, L, L', and M passbands. Also included are a suite of broad order sorting filters (OSFs) for use with the grisms in spectroscopic observations and may eventually be available for imaging observations -- H_wide, K_wide, K_long. Also available are narrow-band imaging filters including Paschen α (1.88 µm), Paschen α continuum (1.90 µm), PAH (3.30 µm), Ice (3.05 µm), L_narrow (3.61 µm), M_narrow (4.81 µm).

Grism spectroscopy is performed with three different grisms, each of which has 3 orders, yielding nearly contiguous coverage from 1 - 5.5 µm. The only gap occurs at the 4.2 - 4.4 µm atmospheric band.

Below is a figure showing the FLITECAM filter pass bands and grism Order Sorting Filters (OSFs) indicated by horizontal bars. The pass bands are overlaid on an atmospheric transmission model based upon the ATRAN code assuming a zenith angle of 45 degrees at an altitude of 41,000 ft, with an H₂O burden of 7 µm.

The following figure illustrates the spectral pass bands provided by each grism and OSF combination. The spectral coverage for each combination is overlaid on a model atmospheric transmission model based upon the ATRAN code assuming a zenith angle of 45 degrees at an altitude of 41,000 ft, with an H₂O burden of 7 µm.

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FLITECAM Sensitivities

Below are shown theoretical sensitivities for a continuum point source, for each of the broadband filter band passes. The Minimum Detectable Continuum Flux (MDCF) in Jy necessary to get S/N = 4 in 900 seconds is plotted atop an ATRAN atmospheric model assuming a zenith angle of 45 degrees at an altitude of 41,000 ft, with an H₂O burden of 7 µm. The bandpass of each filter is shown with a horizontal bar. In some cases, the bar is narrower than the symbol.

In fast imaging mode, using the fastest full frame rate of ~12 frames per second, a S/N of ~4 can be obtained for a K-band magnitude of ~9. Subframe imaging at a rate of 10 kHz can obtain a S/N of ~4 for a source with a

Below is a plot of the FLITECAM spectroscopic sensitivity for a continuum point source across the entire FLITECAM bandpass. The values reported are for a S/N of 4 in 900 seconds at a water vapor overburden of 7 µm, assuming an altitude of 41,000 feet and a 45 degree zenith angle. In the background, an ATRAN atmospheric transmission model using these parameters is plotted in light blue.

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FLITECAM Observation Preparation and Data Handling

Once the observatory has been fully commissioned, additional information will be provided, including a full accounting of overheads associated with particular instrument set-ups and observing strategies; information on preparing observations using the SPT; and details regarding data formatting, calibration and reduction.

Those interested in proposing for observing time during SOFIA Cycle 1 and in preparing successful observations with FLITECAM should carefully read the Cycle 1 Call for Proposals and the Cycle 1 Observer's Handbook, both of which are available from the Cycle 1 page. Users are encouraged to check back regularly on the Cycle 1 page to ensure that they have the most up-to-date version of the Observer's Handbook.

Those wishing to design FLITECAM imaging mode observations for Cycle 1 should use SITE. An exposure time calculator for grism mode observations is available on the FLITECAM Grism Observation Calculator page.

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Disclaimer

All sensitivity and resolution data are preliminary, and based on anticipated performance of the observatory and the instrument.  Actual performance of the SOFIA telescope and instrument combination will be established after flight operations begin.  Telescope performance is expected to be upgraded during the first two years, and instrument performance may be upgraded, or additional modes or capabilities may be added.

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Additional References:

Smith & McLean, "Grism spectroscopy with FLITECAM," Ground-based and Airborne Instrumentation for Astronomy, Ian S. McLean & Masanori Iye, Editors, Proc. SPIE 6269, 62691I (2006), DOI: 10.1117/12.672174

McLean et al., "FLITECAM: a 1-5 micron camera and spectrometer for SOFIA," Ground-based and Airborne Instrumentation for Astronomy, Ian S. McLean & Masanori Iye, Editors, Proc. SPIE 6269, 62695B (2006), DOI: 10.1117/12.672173 [pdf]

Mainzer et al., "Characterization of FLITECAM: the first light camera for SOFIA," Airborne Telescope Systems II, Ramsey K. Melugin & Hans-Peter Roeser, Editors, Proc. SPIE 4857, 21 (2003), DOI: 10.1117/12.458635 [pdf]

Smith & McLean, "Ground-based commissioning of FLITECAM," Ground-based and Airborne Instrumentation for Astronomy II, Ian S. McLean & Mark M. Casali, Editors, Proc. SPIE 7014, 701411 (2008), DOI: 10.1117/12.788693 [pdf]