The Lowell Discovery Telescope (LDT, formerly known as the DCT) is a 4.3-m telescope designed and constructed for optical and near infrared astronomical observation. We present the evolution over time of LDT’s image quality and ways to improve it, upgrades to the instrument suite, and lessons learned from operating during the pandemic.
KEYWORDS: Stray light, Telescopes, Optical coatings, Infrared radiation, Mirrors, Reflectivity, Space telescopes, Neodymium, Infrared telescopes, System on a chip
Effective stray light control is a key requirement for wide dynamic range performance of scientific optical and infrared systems. SOFIA now has over 325 mission flights including extended southern hemisphere deployments; science campaigns using 7 different instrument configurations have been completed. The research observations accomplished on these missions indicate that the telescope and cavity designs are effective at suppressing stray light. Stray light performance impacts, such as optical surface contamination, from cavity environment conditions during mission flight cycles and while on-ground, have proved to be particularly benign. When compared with earlier estimates, far fewer large optics re-coatings are now anticipated, providing greater facility efficiency.
We present a performance report for FLITECAM, a 1-5 μm imager and spectrograph, upon its acceptance and delivery to SOFIA (Stratospheric Observatory for Infrared Astronomy). FLITECAM has two observing configurations: solo configuration and “FLIPO” configuration, which is the co-mounting of FLITECAM with the optical instrument HIPO (PI E. Dunham, Lowell Observatory). FLITECAM was commissioned in the FLIPO configuration in 2014 and flew in the solo configuration for the first time in Fall 2015, shortly after its official delivery to SOFIA. Here we quantify FLITECAM’s imaging and spectral performance in both configurations and discuss the science capabilities of each configuration, with examples from in-flight commissioning and early science data. The solo configuration (which comprises fewer warm optics) has better sensitivity at longer wavelengths. We also discuss the causes of excess background detected in the in-flight FLITECAM images at low elevations and describe the current plan to mitigate the largest contributor to this excess background.
KEYWORDS: Exoplanets, Observatories, Photometry, Stars, Data modeling, Infrared astronomy, Rayleigh scattering, Signal to noise ratio, Point spread functions, Planets
Here, we report on the first successful exoplanet transit observation with the Stratospheric Observatory for Infrared Astronomy (SOFIA). We observed a single transit of the hot Jupiter HD 189733 b, obtaining two simultaneous primary transit lightcurves in the B and z′ bands as a demonstration of SOFIA’s capability to perform absolute transit photometry. We present a detailed description of our data reduction, in particular, the correlation of photometric systematics with various in-flight parameters unique to the airborne observing environment. The derived transit depths at B and z′ wavelengths confirm a previously reported slope in the optical transmission spectrum of HD 189733 b. Our results give new insights to the current discussion about the source of this Rayleigh scattering in the upper atmosphere and the question of fixed limb darkening coefficients in fitting routines.
We present a status report and early commissioning results for FLITECAM, the 1-5 micron imager and spectrometer for
SOFIA (the Stratospheric Observatory for Infrared Astronomy). In February 2014 we completed six flights with
FLITECAM mounted in the FLIPO configuration, a co-mounting of FLITECAM and HIPO (High-speed Imaging
Photometer for Occultations; PI Edward W. Dunham, Lowell Observatory). During these flights, the FLITECAM modes
from ~1-4 μm were characterized. Since observatory verification flights in 2011, several improvements have been made
to the FLITECAM system, including the elimination of a light leak in the FLITECAM filter wheel enclosure, and
updates to the observing software. We discuss both the improvements to the FLITECAM system and the results from the
commissioning flights, including updated sensitivity measurements. Finally, we discuss the utility of FLITECAM in the
FLIPO configuration for targeting exoplanet transits.
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