We discuss the final assembly, integration, and testing of the Star-Planet Activity Research CubeSat. SPARCS is a 6U CubeSat mission designed to monitor the dual-channel, far-UV (153-176 nm) and near-UV (258-308 nm) photometric activity of nearby low mass stars to advance our understanding of their evolution, activity, and the habitability of surrounding exoplanets. This paper details the assembly of the SPARCS instrument and the testing process to characterize and validate the performance of the payload prior to spacecraft integration. To test SPARCS, we have established a customized CubeSat AIT laboratory and thermal vacuum chamber at ASU equipped to handle CubeSats requiring meticulous contamination control for work in the FUV. After a brief overview of these facilities and the testing plan, we will detail the methods and data used to verify the performance of SPARCS and generate calibration products to reduce raw flight data to high-quality science products. The result will be the delivery of the first highly sensitive FUV astrophysics CubeSat which will inform exoplanet environments and future observations of these systems by facilities like the Habitable Worlds Observatory.
The Start-Planet Activity Research CubeSat (SPARCS) is a NASA-funded mission led by Arizona State University, devoted to characterizing the UV emission of low-mass stars. During its nominal one-year mission, SPARCS will observe close to 20 low-mass stars, with the goal of understanding their short and long-term UV variability. SPARCS will be ready for launch in 2025. SPARCS’ payload is a 9-cm telescope paired with two delta-doped charge-coupled devices (CCDs). The data calibration converts the raw instrument counts into an average flux within the two ultraviolet bands (153 - 171 nm, 258 - 308 nm). While the system is only weakly sensitive in the infrared, the target stars are very bright at long wavelengths. This requires careful correction of the data for out-of-band emission. The system is being fully characterized on the ground to provide supporting calibration data. The calibration uses observations of very stable white dwarfs to achieve the 10% photometric accuracy requirement in both bands.
The Star-Planet Activity Research CubeSat (SPARCS) is 6U CubeSat whose mission will be to observe low-mass stars in two ultraviolet (UV) bands. SPARCS will provide time-dependent spectral slope, intensity, and evolution of stellar radiation with the goal of understanding the short- and long-term variability of these targets.
Here we summarize the performance of SPARCam, the science camera for SPARCS. SPARCam is a two-detector camera system allowing independent commanding of two delta-doped, UV CCD47-20 detectors, separately optimized for the SPARCS near UV (NUV) and far UV (FUV) bands. The manuscript includes an overview of the UV detectors optimization and performance as well as a brief description of the camera electronics.
SPARCam was developed by the Jet Propulsion Laboratory and delivered to Arizona State University in October 2023.
The Carbon Plume Mapper (CPM) instrument is a high-fidelity imaging spectrometer developed to pinpoint, quantify, and track methane (CH4) and carbon dioxide (CO2) point source emissions. CPM is an optically fast F/1.8 Dyson spectrometer that operates over the spectral range of 400 – 2500 nm with a spectral sampling of 5.0 nm. Three diffraction grating designs were measured in a testbed to provide a reliable prediction of grating performance in a Dyson system to inform CPM grating design. This paper will detail the gratings, testbed design, measurement process, and data used to assess grating efficiency through wavelength (500-1700 nm) of three grating designs, both full aperture and sub-aperture for two field angles, polarized and unpolarized.
The star-planet activity research CubeSat (SPARCS) is a small space telescope tasked with monitoring sunspots and flares of M-type stars in near ultra-violet (NUV) and far-ultraviolet (FUV) wavelengths. The SPARCS instrument is approaching its critical design review (CDR), and the team is moving forward with assembly integration and test (AI&T) plans for the payload and spacecraft. This paper focuses on the SPARCS thermal vacuum (TVAC) testing facility and thermal testing plan for the payload. The SPARCS TVAC testing chamber has been developed at Arizona State University (ASU) to provide a clean and relevant thermal environment for testing CubeSats and their payloads. The chamber can perform long-duration bakeouts at +80°C for cleaning and monitoring volatile and condensable contaminants with a thermal quartz crystal microbalance (TQCM) and a residual gas analyzer (RGA). These capabilities allow the SPARCS team to control and monitor the cleanliness of the test environment. An FUV monochromator is mounted to the side of the chamber, providing a calibrated light source to test and calibrate the payload. The SPARCS payload will be the first instrument tested in this chamber and demonstrate the capabilities of the SPARCS TVAC Test Facility. The team will verify the payload’s thermal capabilities, such as heating critical surfaces to expel contaminants and cooling the detectors for imaging. The thermal test plan details thermal cycling, hot/cold dwells, thermal balance, and instrument operations through the test. The SPARCS payload TVAC test aims to verify various performance requirements before integration with the spacecraft.
UV-SCOPE is a mission concept to determine the causes of atmospheric mass loss in exoplanets, investigate the mechanisms driving aerosol formation in hot Jupiters, and study the influence of the stellar environment on atmospheric evolution and habitability. As part of these investigations, the mission will generate a broad-purpose legacy database of time-domain ultraviolet (UV) spectra for nearly 200 stars and planets. The observatory consists of a 60 cm, f/10 telescope paired to a long-slit spectrograph, yielding simultaneous, almost continuous coverage between 1203 Å and 4000 Å, with resolutions ranging from 6000 to 240. The efficient instrument provides throughputs < 4% (far-UV; FUV) and < 15% (near-UV; NUV), comparable to HST/COS and much better than HST/STIS, over the same spectral range. A key design feature is the LiF prism, which serves as a dispersive element and provides high throughput even after accounting for radiation degradation. The use of two delta-doped Electron-Multiplying CCD detectors with UV-optimized, single-layer anti-reflection coatings provides high quantum efficiency and low detector noise. From the Earth-Sun second Lagrangian point, UV-SCOPE will continuously observe planetary transits and stellar variability in the full FUV-to-NUV range, with negligible astrophysical background. All these features make UV-SCOPE the ideal instrument to study exoplanetary atmospheres and the impact of host stars on their planets. UV-SCOPE was proposed to NASA as a Medium Explorer (MidEx) mission for the 2021 Announcement of Opportunity. If approved, the observatory will be developed over a 5-year period. Its primary science mission takes 34 months to complete. The spacecraft carries enough fuel for 6 years of operations.
The Star-Planet Activity Research CubeSat (SPARCS) 1 far ultra-violet (FUV) instrument will be tested and thermally characterized in a thermal vacuum (TVAC) chamber. The development and understanding of the thermal characteristics of the TVAC system are crucial to the verification of the thermal capabilities of the SPARCS payload. A TVAC chamber for testing FUV CubeSat instruments is in development at Arizona State University (ASU). The chamber will be used to test the SPARCS payload and future CubeSat missions. A thermal model of the thermal chamber has been developed for use with the SPARCS payload to correlate the model to test data. Correlating the model to test data will provide more realistic temperature predictions and reduce risk to the mission. The chamber model will be used along with the payload thermal model to determine preliminary test procedures creating a more realistic timeline for the testing.
The Star-Planet Activity Research CubeSat (SPARCS) is a 6U CubeSat under construction that is devoted to the photometric monitoring of M stars in the far-UV (FUV) and near-UV (NUV), to measure the time-dependent spectral slope, intensity and evolution of low-mass star high-energy radiation. We report on the progress made in the assembly, integration and test of the instrument payload at Arizona State University using a custom TVAC chamber and optical stimulus that provides calibration light sources and the custom contamination control environment that the FUV demands. The payload consists of a custom 90mm clear aperture telescope developed by Hexagon/Sigma Space, combined with a dichroic plate to separate the FUV and NUV beams developed by Teledyne Acton and Materion, married with twin focal plane array cameras separately optimized for their bandpasses as developed by JPL.
The Star-Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat whose mission will be to observe M stars in two ultraviolet (UV) bands—SPARCS far UV (S-FUV: 153-171 nm) and SPARCS near UV (S-NUV: 260-300 nm). SPARCS would be the first mission to provide time-dependent spectral slope, intensity and evolution of M dwarf stellar radiation; measurements that are critical to deciphering observations of planetary atmosphere from missions such as JWST. The baseline UV camera for SPARCS (SPARCam) includes the electronics boards and two UV detectors, one optimized for each of the SPARCS bands. The camera’s low-noise electronics are based on JPL’s compact, modular design and provide dynamic observation capabilities. For its detectors, SPARCam uses 2D-doped (i.e. delta-doped) CCDs for both channels. Here we present SPARCam development and characterization results prior to payload integration. Copyright 2019. All rights reserved.
Far-infrared astronomy has advanced rapidly since its inception in the late 1950s, driven by a maturing technology base and an expanding community of researchers. This advancement has shown that observations at far-infrared wavelengths are important in nearly all areas of astrophysics, from the search for habitable planets and the origin of life to the earliest stages of galaxy assembly in the first few hundred million years of cosmic history. The combination of a still-developing portfolio of technologies, particularly in the field of detectors, and a widening ensemble of platforms within which these technologies can be deployed, means that far-infrared astronomy holds the potential for paradigm-shifting advances over the next decade. We examine the current and future far-infrared observing platforms, including ground-based, suborbital, and space-based facilities, and discuss the technology development pathways that will enable and enhance these platforms to best address the challenges facing far-infrared astronomy in the 21st century.
KEYWORDS: Ultraviolet radiation, Stars, Atmospheric modeling, Space operations, Space telescopes, Planets, Telescopes, Sensors, Exoplanets, Control systems
Roughly 40 billion M dwarfs in our galaxy host at least one small planet in the habitable zone (HZ). The stellar ultraviolet (UV) radiation from M dwarfs is strong and highly variable, and impacts planetary atmospheric loss, composition and habitability. These effects are amplified by the extreme proximity of their HZs (0.1–0.4 AU). Knowing the UV environments of M dwarf planets will be crucial to understanding their atmospheric composition and a key parameter in discriminating between biological and abiotic sources for observed biosignatures. The Star-Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to photometric monitoring of M stars in the far-UV and near-UV, measuring the time-dependent spectral slope, intensity and evolution of low-mass star high-energy radiation.
Here we discuss high-performance UV detectors to be used with the planned Star-Planet Activity Research CubeSat (SPARCS). SPARCS is a 6U cubesat designed to monitor M stars (0.1 – 0.6 solar masses) in two photometric bands in the near UV and far UV (S-NUV, 260-300 nm; S-FUV, 150-170 nm). SPARCS targets range in mass and age, including young stars (10-20 Myr), which are likely forming terrestrial planets, to old stars with known transiting planets, allowing us to map the evolution of UV emission and flare rates. The spectral slope, variability and evolution of a host star’s highenergy radiation would provide realistic input stellar fluxes to planet atmospheric models, which would aide in understanding the evolution and habitability of a planet and in interpreting its transmission and emission spectrum. The baseline S-NUV detector is a 2D-doped (delta-doped or superlattice-doped) charge coupled device (CCD) optimized with a custom antireflection (AR) coating to achieve quantum efficiency (QE)>70% throughout the S-NUV band. The SNUV detector would be coupled with a stand-alone red-blocking filter that provides at least three orders of magnitude (i.e., ≥OD3) out-of-band suppression, critical for the observations of such cool, red stars. Their combined throughput would be >25% (peak) in the S-NUV. The baseline S-FUV detector is a 2D-doped CCD optimized for the S-FUV band; it includes an integrated filter designed to maximize in-band throughput with good red-leak suppression. As designed, the solar-blind silicon detector achieves peak QE>35% in the S-FUV band and ≥OD2 out-of-band suppression. SPARCS has baselined a dichroic design that allows for simultaneous S-NUV and S-FUV observation. SPARCS would advance 2D-doped detectors and detector-integrated out-of-band-rejection filter technologies for their potential application in future mission concepts such as LUVOIR and HabEx.
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