CUTE Spacecraft

Characterize the composition and mass-loss rates of exoplanet atmospheres.

Use near-ultraviolet (NUV) transmission spectroscopy from 255 to 330 nanometers (nm) to characterize the composition and mass-loss rates of exoplanet atmospheres. CUTE measures how the NUV light from the host star is changed as the exoplanet transits in front of the star and passes through the planet’s atmospheres. CUTE’s spectrally resolved lightcurve will provide constraints on the composition and escape rates of these atmospheres, and may provide the first concrete evidence for magnetic fields on extrasolar planets.

The mission goal is to train and educate students while conducting scientific research. This mission is similar to the CSSWE, MinXSS‐1, MinXSS‐2 and CSIM, which have gathered over 100 MB of data from amateur operators and were coordinated by the IARU. As has been the case in the past, we will be actively soliciting the telemetry from amateurs. The information provided by amateurs has been crucial for past missions, enabling us to detect instrument orbits and the Doppler‐shifted communication frequencies and troubleshoot anomalies. It is common for all of our missions to have extensive student involvement during the design, building, testing, and operation of the instrument.

CUTE captured ~50 scientifically viable transits from 6 exoplanets despite frequent sun-point regressions.

The first NASA-funded small satellite for exoplanet science is continuing to gather data well beyond its expected lifetime. CUTE was designed to operate in space for at least eight months. Twenty-seven months later, the satellite’s onboard instruments still are observing the dramatic atmospheric loss of “hot jupiters,” gas giants orbiting very close to bright stars. CUTE remains operational more than two years after launch thanks to ingenuity and luck.

Since its launch, CUTE has experienced an unusually high frequency of ADCS-driven safe mode events, occurring up to three times per week. An investigation into the issue revealed the frequent safe mode events to be due to a timing issue of the Inertial Measurement Unit (IMU) information packets before being sent to the Guidance, Navigation and Control system (GNC). This issue is described as a “glitch” due to the sudden jump discontinuity in certain spacecraft telemetry data following an IMU timing issue. Telemetry analysis revealed significant discrepancies between commanded and reported attitude quaternions, casting doubt on the spacecraft's reported attitude and telemetry values during these glitch events. By conducting a thorough analysis of Sun sensor photodiode counts, battery cycles, spacecraft body rate, and magnetic field vectors, we concluded that the spacecraft's reported quaternions did not accurately reflect its actual orientation following the glitch events. The team utilized basic attitude determination methods, such as integrating the spacecraft's body rate, to further approximate its attitude around the glitches. This calculated attitude revealed that, at times, the glitch was causing the spacecraft's telescope to partially orient towards the Sun, likely leading to the degradation of the primary science instrument over time.

Since launch, the sensitivity of CUTE’s optics have fallen faster than expected. CUTE’s telescope optics are coated with Aluminum and protected with a thin layer of MgF2 to prevent or slow the rate of the formation of Al2O3, which absorbs UV light rather than reflecting it. Exposure to UV light, such as that coming from the Sun, can significantly accelerate the growth of an Al2O3 layer (Robert F. Berg, 2023). As the glitches cause the CUTE primary mirror to be exposed to the Sun, the CUTE team suspects that these glitches are the driving factor of the accelerated degradation of the instrument’s sensitivity. This reduces the number of astronomical objects available for CUTE to observe. Nonetheless, it is also possible that CUTE’s loss of effective area could be due to the use of a bare-Al grating, rather than an MgF2-protected grating, or other sources of contamination and degradation.

• PLATFORM - Blue Canyon

• Cesium Satellite 1
• Cesium Satellite 2
• CuPID
• CUTE