Abstract
The Transiting Exoplanet Survey Satellite (TESS) is an MIT-led, NASA-funded Explorer-class planet finder launched in April 2018. TESS will carry out a 2-year all-sky survey with the primary goal of detecting small transiting exoplanets around bright and nearby stars. The TESS instrument consists of four wide-field cameras in a stacked configuration, providing a combined field of view of 24 deg × 96 deg that spans approximately from the ecliptic plane to the ecliptic pole. In order to achieve the desired photometric precision necessary for the mission, TESS uses the instrument cameras as star trackers during fine-pointing mode to enhance attitude accuracy and stabilization for science operations. We present our approach in quantifying the expected performance of the fine-pointing system and assessing the impact of pointing performance on the overall photometric precision of the mission. First, we describe the operational details of the fine-pointing system with the science instrument being used for star-tracking. Next, we present the testing framework used to quantify the attitude determination performance of the system and the expected attitude knowledge accuracy results, both in coarse-fine pointing hand-off and in nominal fine-pointing conditions. By combining simulations of the instrument and the spacecraft bus, we quantify the closed-loop fine-pointing stability performance of the system in nominal science operations as well as in the case of camera unavailability due to Earth/Moon interference. Finally, we assess the impact of platform pointing stability on the photometric precision of the system using detailed system modeling and discuss the applicability of mitigation techniques to reduce the effect of jitter on TESS science data.
Highlights
1.1 Transiting Exoplanet Survey SatelliteThe Transiting Exoplanet Survey Satellite (TESS) is a 2-year all-sky survey mission looking for transiting exoplanets around bright and nearby stars.[1,2] TESS is the natural successor to the highly-successful Kepler mission, which has enabled significant advancements in exoplanet sciences.[3]
The results show that the jitter level does not change relative to centroid error for error levels below 0.1 pixel, which is achieved in most nominal cases. (The average 1σ centroid error of a 9th magnitude star under nominal spacecraft disturbances and background noise sources is ∼0.07 pixel.) Extensive testing and analysis by Orbital ATK has established that the limiting factor of the closed-loop finepointing performance is the reaction wheel readout noise
The jitter curve is highly dependent on the size of the optimal aperture in each case, which becomes smaller with dimmer stars
Summary
The Transiting Exoplanet Survey Satellite (TESS) is a 2-year all-sky survey mission looking for transiting exoplanets around bright and nearby stars.[1,2] TESS is the natural successor to the highly-successful Kepler mission, which has enabled significant advancements in exoplanet sciences.[3]. The orbit of TESS is a high-Earth, 2:1 lunar-resonant orbit, a low-cost, and stable orbit option that is capable of providing a relatively unobstructed view of the celestial sphere.[5] The final elliptical orbit has a 13.7-day period with a nominal perigee at 17 RÈ and apogee at 59 RÈ, achieved by a series of apogeeraising and perigee-raising burns and a lunar gravity assist.[2,5] The mission operational modes include the low altitude housekeeping operations (LAHO) near perigee and the high altitude science operations (HASO) for the remaining portion of the orbit. The TESS instrument, developed primarily by MIT and MIT Lincoln Laboratory, consists of an Alternate Data Handling Unit (ADHU) and four identical refractive cameras. The TESS spacecraft bus is based on the LEOStar-2, a flexible high-performance platform with space-heritage developed by Orbital ATK. Previous missions that have used the LEOStar-2 bus include SORCE, GALEX, AIM, NuSTAR, and others.[7] The TESS spacecraft total launch mass is 350 kg with deployed configuration dimensions of ∼3.9 m × 1.5 m.7. The spacecraft attitude control system provides three-axis stabilization using a two-headed star tracker, an inertial reference unit, and a four-wheel zero-momentum system.[7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
