GRBAlpha is a 1U CubeSat launched in March 2021 to a sun-synchronous LEO at an altitude of 550 km to perform an in-orbit demonstration of a novel gamma-ray burst detector developed for CubeSats. VZLUSAT-2 followed ten months later in a similar orbit carrying as a secondary payload a pair of identical detectors as used on the first mission. These instruments detecting gamma-rays in the range of 30-900 keV consist of a 56 cm2 5 mm thin CsI(Tl) scintillator read-out by a row of multi-pixel photon counters (MPPC or SiPM). The scientific motivation is to detect gamma-ray bursts and other HE transient events and serve as a pathfinder for a larger constellation of nanosatellites that could localize these events via triangulation.
At the beginning of July 2024, GRBAlpha detected 140 such transients, while VZLUSAT-2 had 83 positive detections, confirmed by larger GRB missions. Almost a hundred of them are identified as gamma-ray bursts, including extremely bright GRB 221009A and GRB 230307A, detected by both satellites. We were able to characterize the degradation of SiPMs in polar orbit and optimize the duty cycle of the detector system also by using SatNOGS radio network for downlink.
KEYWORDS: Sensors, Satellites, Computer aided design, Gamma radiation, Analog electronics, Solar cells, Control systems, Signal detection, Scintillators, Infrared sensors
Since transient events, such as gamma-ray bursts (GRBs), can be expected from any direction at any time, their detection and localization is difficult. For localizing transient events, we proposed the Cubesats applied for measuring and localising transients mission (CAMELOT), which will be a fleet of nanosatellites distributed evenly on low Earth orbits. As the first step, we designed a technical demonstration for the CAMELOT mission, named GRBAlpha. Even though this 1U satellite has a reduced size scintillator and different mechanical constraints, all the electronic subsystems and communication protocols are the same. GRBAlpha is operating in orbit since 2021 March 22 and it already detected numerous confirmed GRBs. For further details of the early results and ongoing operations see the related presentation at this conference. After this first success, we continue with the design of the 3U prototype of the CAMELOT satellite, which will host an eight times larger detector system integrated into two walls of the satellite. The main difference is the mechanical constraints of mounting the detector in its casing. While for GRBAlpha the reduced sized scintillator is located on the top (Z+) side of the satellite, for CAMELOT it is located on two of the sides. Since the CubeSat standard does not allow enough lateral extension on the sides, the casing has to be sunk into the satellite where it could interfere with the standard PC/104 stacking. Here, we present a solution on how to integrate the scintillator casing, the uniquely designed electronics and commercially available satellite subsystems.
We present the detector performance and early science results from GRBAlpha, a 1U CubeSat mission, which is a technological pathfinder to a future constellation of nanosatellites monitoring gamma-ray bursts (GRBs). GRBAlpha was launched in March 2021 and operates on a 550 km altitude sun-synchronous orbit. The gamma-ray burst detector onboard GRBAlpha consists of a 75×75×5 mm CsI(Tl) scintillator, read out by a dual-channel multi-pixel photon counter (MPPC) setup. It is sensitive in the ∼30−900 keV range. The main goal of GRBAlpha is the in-orbit demonstration of the detector concept, verification of the detector’s lifetime, and measurement of the background level on low-Earth orbit, including regions inside the outer Van Allen radiation belt and in the South Atlantic anomaly. GRBAlpha has already detected five, both long and short, GRBs and two bursts were detected within a time-span of only 8 hours, proving that nanosatellites can be used for routine detection of gamma-ray transients. For one GRB, we were able to obtain a high resolution spectrum and compare it with measurements from the Swift satellite. We find that, due to the variable background, the time fraction of about 67% of the low-Earth polar orbit is suitable for gamma-ray burst detection. One year after launch, the detector
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.