ASTERIA during testing. It is a 6U CubeSat space telescope for the detection of exoplanets
|Mission type||Technology demonstrator|
|Mission duration||Nominal: 90 days|
Extension: up to 1 year (proposed)
|Manufacturer||JPL and MIT|
|Launch mass||12 kg (26 lb)|
|Dimensions||10 cm × 20 cm × 30 cm (0.33 ft × 0.66 ft × 0.98 ft)|
|Start of mission|
|Launch date||August 14, 2017, 16:31 UTC|
deployed: 20 November 2017
|Launch site||Kennedy LC-39A|
|End of mission|
|Last contact||5 December 2019|
|Semi-major axis||6,775 kilometres (4,210 miles)|
|Periapsis altitude||402.7 kilometres (250.2 miles)|
|Apoapsis altitude||406.7 kilometres (252.7 miles)|
|Wavelengths||visible spectrum: 390–700 nm|
ASTERIA (Arcsecond Space Telescope Enabling Research in Astrophysics) is a miniaturized space telescope meant as a technology demonstrator to advance the capabilities for astrophysical measurements. Its bus is a nanosatellite of the 6U CubeSat format. It was designed in collaboration between the Massachusetts Institute of Technology (MIT) and NASA's Jet Propulsion Laboratory, and served as an introductory flight project for early-career hires.
ASTERIA was launched on 14 August 2017 and deployed into low Earth orbit from the International Space Station on 20 November 2017. The primary mission lasted 90 days, but the satellite continued operation for two years before ceasing contact with ground station operators. The last successful communications were made on December 5, 2019. The Principal Investigator was Canadian-American astronomer and planetary scientist Sara Seager, from the Massachusetts Institute of Technology.
The Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) is a six-unit (6U) CubeSat space telescope deployed from the International Space Station (ISS) with the goal of testing new technologies for the detection of exoplanets using the transit method. The program was funded at JPL through the Phaeton Program for training early career employees. Its target mission lasted for 90 days, after which it was extended until the loss of contact with the spacecraft. 
ASTERIA's capabilities enabled precision photometry to be performed on an opportunistic basis to study stellar activity, transiting exoplanets, and other astrophysical phenomena. The technological objectives of the mission were "to achieve arcsecond-level line of sight pointing error, and highly stable focal plane temperature control for precision photometry" as a way to detect transiting exoplanets, and characterize their host stars. The pointing stability was demonstrated over 20-minute observations. Pointing repeatability would be determined over a minimum of five observations over eight or more days, with the target star being returned to the same position on the focal plane by adjusting the spacecraft orientation and focal plane position.
This mission may serve as a pathfinder for a fleet of low-cost space telescopes observing multiple targets at once to refine long-term mission goals by identifying new objects for other telescopes to observe. The miniaturization of a photometric detection system into a CubeSat could enable a constellation of multiple orbiting observatories for a continuous study of the brightest Sun-like stars which is not possible by conventional space observatories given their cost. Having one or more CubeSats pointed at a target star for extended duration could reveal long-transiting exoplanets. This mission also provided additional information in the design of future space telescopes.
ASTERIA was launched on board a SpaceX Falcon-9 rocket (mission SpaceX CRS-12) on 14 August 2017 and it was deployed to low Earth orbit from the International Space Station on November 2017. A crew member in the ISS transferred the satellite from the cargo vehicle to the Japanese Experiment Module (JEM) airlock for transfer outside the ISS.
The ASTERIA concept is a follow-on to the proposed 3U CubeSat mission called ExoplanetSat that was designed in the early 2010s. The ASTERIA telescope is a 6U CubeSat measuring 10 × 20 × 30 cm, and has a mass of 12 kg (26 lb). Power is supplied by deployable fixed solar panels and rechargeable batteries.
Commercial reaction wheels provide coarse orientation (attitude control), while fine pointing control is achieved by tracking a set of guide stars on the active pixel sensor (CMOS) and moving the piezoelectric positioning stage to compensate for residual pointing errors. The goal is to maintain the target star image to within a fraction of a detector pixel over long durations, with a pointing accuracy better than 60 arcsecond, and optimally as precise as 5 arcsecond over a period of 20 minutes. The gain of each pixel is temperature sensitive, so the second objective of ASTERIA is to demonstrate milliKelvin-level temperature stability of the imaging detector.
ASTERIA demonstrated the ability to collect photometric data, and process photometric light curves from a CubeSat. Secondary applications included measuring stellar rotation periods, characterizing stellar activity of exoplanet hosts, and supporting ground-based radial velocity measurements with simultaneous photometry. After the success of its 90 day planned mission, ASTERIA's extended mission targeted bright stars (luminosity Vmag < 8) with known low-mass planets discovered by the radial velocity method, that are not yet known to transit.
The telescope payload consists of a lens and baffle assembly, a CMOS imager, and a two-axis piezoelectric positioning stage on which the focal plane is mounted. The optics section is composed of a f/1.4 85 mm Zeiss lens with a 28.6-degree field of view and six elements, focusing an image 43 mm in diameter onto the focal plane. The focal plane array houses two active detector areas – one larger CMOS detector that fulfills the science function, and a smaller CMOS sensor to act as a rapid-cadence star camera to provide orientation data to the attitude control system.
In April 2018 NASA's JPL reported that ASTERIA "has accomplished all of its primary mission objectives, demonstrating that the miniaturized technologies on board can operate in space as expected."
- Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA). Jon Nelson, Jet Propulsion Laboratory, NASA.
- "Tiny Satellite for Studying Distant Planets Goes Quiet". JPL.
- ISS - ASTERIA. Victor M. Escobedo Jr. NASA News, October 2017.
- ASTERIA. Gunter Krebs, Gunter's Space Page. 14 August 2017.
- ASTERIA Satellite. Spaceflight 101 18 November 2017.
- Sara Seager- Exoplanet Space Missions. 2017.
- ExoplanetSat: A Nanosatellite Space Telescope for Detecting Transiting Exoplanets (PDF). Matthew W. Smith, Sara Seager, Christopher M. Pong, SungyungLim, Matthew W. Knutson, Timothy C. Henderson, Joel N. Villaseñor, Nicholas K. Borer, David W. Miller, Shawn Murphy. Massachusetts Institute of Technology. CubeSat Developers' Workshop. April 20–22, 2011. San Luis Obispo, CA
- Characterization of CubeSat Reaction Wheel Assemblies (PDF). Joel Shields, Christopher Pong, Kevin Lo, Laura Jones, Swati Mohan, Chava Marom, Ian McKinley, William Wilson and Luis Andrade. Journal of Small Satellites, Vol. 6, No. 1, pp. 565–580. 2017.
- Astrophysics CubeSat Demonstrates Big Potential in a Small Package. Jet Propulsion Laboratory, NASA. 12 April 2018.