In the world of astronomy, space telescopes are celebrated for their size. Even before it launches to space, the James Webb Telescope was showing off its massive 21 feet-wide, 4-inch-thick mirror.
However, a tiny spacecraft is proving that size doesn't always matter when it comes to observing the vast universe. A briefcase-sized satellite named ASTERIA just broke the record for the smallest satellite to detect an exoplanet.
The detection is detailed in a study that was recently accepted for publication in the Astronomical Journal.
ASTERIA, short for Arcsecond Space Telescope Enabling Research in Astrophysics, wasn't initially designed to perform any science. Instead, the CubeSat, a type of miniaturized satellite made up of multiples of 10 cm × 10 cm × 10 cm cubic units, was launched to research new capabilities for future missions.
Therefore, the tiny satellite only had one job; fine pointing control or the ability to stay very steadily focused on an object for a long period of time.
But ASTERIA seemingly had bigger dreams than that; the satellite wanted to prove to itself and the rest of its miniature comrades that small satellites can perform complex tasks in space.
The CubeSat used its fine pointing control technique to detect exoplanet 55 Cancri e, a super-Earth planet that's about twice the size of Earth and orbits extremely close to its host star.
ASTERIA found this scorching hot exoplanet through the transit method, whereby scientists look for dips in the light of a star caused by a planet crossing their view of its host star.
"Detecting this exoplanet is exciting, because it shows how these new technologies come together in a real application," Vanessa Bailey, the principal investigator for ASTERIA's exoplanet science team at Jet Propulsion Laboratory, said in a statement.
The exoplanet was originally discovered in the year 2004. And although ASTERIA's detection would not have fully convinced a team of scientists that the exoplanet was there, the satellite made what is called a marginal detection based on faint signals. However, by comparing the data collected by ASTERIA with previous detections of Cancri 55 e, the team of scientists could confirm that it was indeed the same exoplanet they were looking at.
"We went after a hard target with a small telescope that was not even optimized to make science detections - and we got it, even if just barely," Mary Knapp, the ASTERIA project scientist at Massachusetts Institute of Technology's Haystack Observatory and lead author of the study, said in a statement. "I think this paper validates the concept that motivated the ASTERIA mission: that small spacecraft can contribute something to astrophysics and astronomy."
Although ASTERIA is a pioneer in and of itself, the team of engineers behind the CubeSat predict that it could be used more of a sidekick rather than the main act.
It would be nearly impossible to expect the small satellite to perform the same tasks as NASA's main exoplanet hunter, the Transiting Exoplanet Survey Satellite (TESS). However, these miniature spacecraft could monitor a star for a long period of time, or do followup observations of transiting planets.
ASTERIA was launched on August 14, 2017, and originally designed to spend 90 days in space. However, it received three mission extensions before the team lost contact with the tiny satellite in December, 2019. Its legacy will live on in the form of a scorching-hot exoplanet, though.
Abstract: ASTERIA (Arcsecond Space Telescope Enabling Research In Astrophysics) is a 6U CubeSat space telescope (10 cm x 20 cm x 30 cm, 10 kg). ASTERIA's primary mission objective was demonstrating two key technologies for reducing systematic noise in photometric observations: high-precision pointing control and high-stabilty thermal control. ASTERIA demonstrated 0.5 arcsecond RMS pointing stability and ±10 milliKelvin thermal control of its camera payload during its primary mission, a significant improvement in pointing and thermal performance compared to other spacecraft in ASTERIA's size and mass class. ASTERIA launched in August 2017 and deployed from the International Space Station (ISS) November 2017. During the prime mission (November 2017 -- February 2018) and the first extended mission that followed (March 2018 - May 2018), ASTERIA conducted opportunistic science observations which included collection of photometric data on 55 Cancri, a nearby exoplanetary system with a super-Earth transiting planet. The 55 Cancri data were reduced using a custom pipeline to correct CMOS detector column-dependent gain variations. A Markov Chain Monte Carlo (MCMC) approach was used to simultaneously detrend the photometry using a simple baseline model and fit a transit model. ASTERIA made a marginal detection of the known transiting exoplanet 55 Cancri e (∼2~\Rearth), measuring a transit depth of 374±170 ppm. This is the first detection of an exoplanet transit by a CubeSat. The successful detection of super-Earth 55 Cancri e demonstrates that small, inexpensive spacecraft can deliver high-precision photometric measurements.