Session
Weekend Session III: Science/Mission Payloads Research & Academia 1
Location
Utah State University, Logan, UT
Abstract
In recent years, CubeSat projects have initiated plans to conduct astronomical observations by deploying mission payloads. CubeSats present a promising solution for swiftly addressing critical challenges in astrophysics with flexibility. Within Cubeats, where both the bus system and mission payload occupy about half of the volume, there is a necessity to miniaturize mission equipment. The critical factor in astronomical observations, light-gathering ability, is determined not only by the aperture size but, more importantly for diffuse emission, by the optical throughput, i.e., the product of the aperture area and the observing solid angle. Consequently, even with a compact optical system, specializing in wide-field observations enables achieving light-gathering ability equivalent to that of a large-diameter telescope. Therefore, we propose equipping CubeSats with small, wide-field telescopes specialized for observing essential quantities in understanding the cosmic history of star formation, such as extragalactic background Light (EBL), and foreground components like zodiacal light and diffuse galactic light. Radiation from first-generation celestial bodies, which is challenging to detect due to their darkness in the distant universe, is included in the EBL in the visible to near-infrared wavelengths. Hence, wide-field survey observations in the visible and near-infrared play a crucial role in unraveling when, where, and how the first-generation stars were born in the early universe. However, current technology has not enabled the development of CubeSats with mechanisms capable of cooling infrared detectors to temperatures below a few tens of Kelvin. Therefore, we have designed an optical system focusing on the visible EBL. In the astronomical W6U CubeSat mission VERTECS (Visible Extragalactic background RadiaTion Exploration by CubeSat), we are developing a 3U mission payload, comprised of 1U-sized lens optics, camera modules, and baffles each. The lens optical system achieves a high throughput ( > 10-6 m2 sr) by covering the entire field of view with 6 degrees by 6 degrees and each pixel with a field of view of 11 arcseconds by 11 arcseconds. The camera module uses a CMOS sensor with high quantum efficiency in visible light, featuring sufficiently low dark current noise (approximately 0.01 electrons per second at 269 K) and readout noise (approximately 2.6 electrons at 24 dB analog gain), compared to the photocurrent generated by the EBL and foreground photon noise. The baffle is designed to attenuate stray light from the Sun and Earth to negligible levels compared to the EBL signal. Additionally, a set of color filters divides the wavelength range of 400 to 800 nm into four bands. In our observation strategy, we capture 60-second exposure images by shifting the field of view by 3 degrees and perform photometry on the stacked images in the four bands. VERTECS project was selected in JAXA-Small Satellite Rush Program in 2022 and is currently advancing in satellite development, with a scheduled launch in FY2025. Thus far, a significant portion of the mission payload design meets the required specifications, and progress is underway towards the fabrication of the engineering model. In this presentation, we will report on the progress of our optical telescope development, our strategy for visible EBL observations, and our future plans.
Development of a Compact Wide-Field Telescope to be Mounted on VERTECS
Utah State University, Logan, UT
In recent years, CubeSat projects have initiated plans to conduct astronomical observations by deploying mission payloads. CubeSats present a promising solution for swiftly addressing critical challenges in astrophysics with flexibility. Within Cubeats, where both the bus system and mission payload occupy about half of the volume, there is a necessity to miniaturize mission equipment. The critical factor in astronomical observations, light-gathering ability, is determined not only by the aperture size but, more importantly for diffuse emission, by the optical throughput, i.e., the product of the aperture area and the observing solid angle. Consequently, even with a compact optical system, specializing in wide-field observations enables achieving light-gathering ability equivalent to that of a large-diameter telescope. Therefore, we propose equipping CubeSats with small, wide-field telescopes specialized for observing essential quantities in understanding the cosmic history of star formation, such as extragalactic background Light (EBL), and foreground components like zodiacal light and diffuse galactic light. Radiation from first-generation celestial bodies, which is challenging to detect due to their darkness in the distant universe, is included in the EBL in the visible to near-infrared wavelengths. Hence, wide-field survey observations in the visible and near-infrared play a crucial role in unraveling when, where, and how the first-generation stars were born in the early universe. However, current technology has not enabled the development of CubeSats with mechanisms capable of cooling infrared detectors to temperatures below a few tens of Kelvin. Therefore, we have designed an optical system focusing on the visible EBL. In the astronomical W6U CubeSat mission VERTECS (Visible Extragalactic background RadiaTion Exploration by CubeSat), we are developing a 3U mission payload, comprised of 1U-sized lens optics, camera modules, and baffles each. The lens optical system achieves a high throughput ( > 10-6 m2 sr) by covering the entire field of view with 6 degrees by 6 degrees and each pixel with a field of view of 11 arcseconds by 11 arcseconds. The camera module uses a CMOS sensor with high quantum efficiency in visible light, featuring sufficiently low dark current noise (approximately 0.01 electrons per second at 269 K) and readout noise (approximately 2.6 electrons at 24 dB analog gain), compared to the photocurrent generated by the EBL and foreground photon noise. The baffle is designed to attenuate stray light from the Sun and Earth to negligible levels compared to the EBL signal. Additionally, a set of color filters divides the wavelength range of 400 to 800 nm into four bands. In our observation strategy, we capture 60-second exposure images by shifting the field of view by 3 degrees and perform photometry on the stacked images in the four bands. VERTECS project was selected in JAXA-Small Satellite Rush Program in 2022 and is currently advancing in satellite development, with a scheduled launch in FY2025. Thus far, a significant portion of the mission payload design meets the required specifications, and progress is underway towards the fabrication of the engineering model. In this presentation, we will report on the progress of our optical telescope development, our strategy for visible EBL observations, and our future plans.
