The on-orbit performance of the Colorado Ultraviolet Transit Experiment (CUTE) Mission

TL;DR

This paper reports on the on-orbit performance of the CUTE CubeSat, detailing its instrumentation, calibration results, and thermal and pointing stability for ultraviolet transit spectroscopy of exoplanets.

Contribution

It provides the first comprehensive on-orbit performance characterization of the CUTE ultraviolet spectrograph and spacecraft system after launch.

Findings

Effective area of 19.0–27.5 cm²

Average spectral resolution of 2.9 Å

Pointing jitter ≤ 6 arcseconds in over half of exposures

Abstract

We present the on-orbit performance of the Colorado Ultraviolet Transit Experiment ($CUTE$). $CUTE$ is a 6U CubeSat that launched on September 27th, 2021 and is obtaining near-ultraviolet (NUV, 2480 A -- 3306 A) transit spectroscopy of short-period exoplanets. The instrument comprises a 20 cm $\times$ 8 cm rectangular Cassegrain telescope, an NUV spectrograph with a holographically ruled aberration-correcting diffraction grating, and a passively cooled, back-illuminated NUV-optimized CCD detector. The telescope feeds the spectrograph through an 18$'$ $\times$ 60$''$ slit. The spacecraft bus is a Blue Canyon Technologies XB1, which has demonstrated $\leq$ 6$''$ jitter in 56% of $CUTE$ science exposures. Following spacecraft commissioning, an on-orbit calibration program was executed to characterize the $CUTE$ instrument's on-orbit performance. The results of this calibration indicate that the effective area of $CUTE$ is $\approx$ 19.0 -- 27.5 cm$^{2}$ and that the average intrinsic resolution element is 2.9 A across the bandpass. This paper describes the measurement of the science instrument performance parameters as well as the thermal and pointing characteristics of the observatory.