ASTERIA (ASTERIA) - 10.18.17

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
The Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) is a six-unit (6U) CubeSat deployed from the International Space Station (ISS) that tests new technologies for astronomical observation, such as the detection of planets outside our solar system (a.k.a., exoplanets). Observing exoplanets requires repeated observation of stars over a long period of time from a dark environment, so that the small shadow of an orbiting planet can be detected passing through the star’s light. ASTERIA uses advanced pointing control technology, new thermal stabilization features, and the scalable CubeSat-platform to perform these complex measurements.
Science Results for Everyone
Information Pending

The following content was provided by Sara Seager, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom:

Principal Investigator(s)
Sara Seager, Ph.D., Massachusetts Institute of Technology, Cambridge, MA, United States

Co-Investigator(s)/Collaborator(s)
Mary Knapp, Ph.D., Massachusetts Institute of Technology, Cambridge, MA, United States

Developer(s)
NanoRacks, LLC, Webster, TX, United States
NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
National Laboratory (NL)

Research Benefits
Information Pending

ISS Expedition Duration
April 2017 - September 2017

Expeditions Assigned
51/52

Previous Missions
Information Pending

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Experiment Description

Research Overview

The Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) is a technology demonstration, and opportunistic science mission, that advances the state of the art in nanosatellite capabilities for astrophysical measurements. The spacecraft is a 6U CubeSat (roughly 10 × 20 × 30 cm, 10 kg) that operates in low-Earth orbit. The objectives of the project are to achieve arcsecond-level line of sight pointing error, and highly stable focal plane temperature control. These technologies enable precision photometry—i.e. the measurement of the brightness of stars over time. Photometry is compelling because it provides a way to detect transiting exoplanets, and characterize their host stars.
  • A CubeSat space telescope for demonstrating new technologies for studying nearby stars
  • Stabilizes the position of a star image on the telescope detector
  • Returns a star image to the same location on the telescope detector
  • Holds the temperature of the telescope detector constant
  • Downloads images of the star so that its brightness can be observed over time
  • Serves as a pathfinder for a fleet of low-cost space telescopes observing multiple targets at once.

Description

The first objective of the Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) mission is to demonstrate arcsecond-level pointing control both during a single observation, and from one observation to the next. The goal is to maintain the target star image to within a fraction of a detector pixel over long durations. Image motion over the detector pixels can cause variations in the measured brightness, since both the between-pixel (interpixel) and within-pixel (intrapixel) response varies across the detector. By holding the star image to the same fraction a pixel throughout an observation, the technology demonstrated by ASTERIA minimizies instrument-derived photometric variation, and enables more sensitive photometric monitoring of real astrophysical variations in the star.
 
Pointing control is achieved through a two-stage approach. A set of reaction wheels provides coarse three-axis control of the spacecraft body, holding an inertial attitude that points the payload to a target star. Within the payload, a two-axis piezoelectric stage provides an additional level of fine control by making small, rapid adjustments to the detector position to keep the target star stationary.
 
The second objective of ASTERIA is to demonstrate milliKelvin-level temperature stability of the imaging detector. The gain of each pixel is temperature sensitive, so tight thermal control reduces instrumental photometric variation that might otherwise be mistaken as an astrophysical signal. Unlike other space telescopes such as Kepler and Spitzer that reside in an Earth-trailing orbit, ASTERIA is subjected to day/night cycles that occur every 90 minutes in low-Earth orbit. The lack of a stable thermal environment makes active temperature control all the more important.
 
Precision thermal control is achieved by isolating the payload from the spacecraft bus, and passively cooling the detector using a space-facing radiative surface. Thermal sensors and trim heaters located on the detector, act in a closed loop to perform small temperature corrections over the course of an observation, and maintain stability to the required precision.
 
The ASTERIA primary mission is devoted to satisfying the objectives contained in the L1 requirements, specifically the pointing control and thermal control demonstrations. ASTERIA also uses the primary mission to demonstrate the ability to collect photometric data, and process photometric light curves. If programmatic and technical resources remain after the primary mission, an extended mission will be carried out. During this phase, ASTERIA would perform high precision photometry on nearby, bright stars. The extended mission targets bright stars (Vmag < 8) with known, low-mass planets discovered by the radial velocity method, that are not yet known to transit. If a transit is observed, the planet radius can be derived from the depth of the transit, and the bulk density of these planets can be calculated using the mass obtained from radial velocity observations. Transiting planets around bright stars, like the ones observed by ASTERIA, are highly valuable because the atmospheres of these planets can be studied in detail by large telescopes (e.g. Hubble, James Webb Space Telescope, etc.) using spectroscopy. Secondary applications for ASTERIA observation data include measuring stellar rotation periods, characterizing stellar activity of exoplanet hosts, and supporting ground-based radial velocity measurements with simultaneous photometry.
 
ASTERIA traces its roots back to a 3U CubeSat called ExoplanetSat, originally developed at the Massachusetts Institute of Technology (MIT) with contributions from NASA, Draper Laboratory, and the Jet Propulsion Laboratory (JPL). ASTERIA was developed and built at JPL, and funded by the JPL Phaeton Program for training early career employees. Mission operations conducted from JPL use a ground station at Morehead State University.

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Applications

Space Applications
ASTERIA’s updated thermal and sensor technology expands the range of space where small telescopes can operate effectively, and provide additional information in the design of future observational platforms. ASTERIA also demonstrates an application wherein the distributed, scalable capacities of CubeSats can be used to solve a large-scale remote sensing problem. The photometric study of bright nearby stars contributes to a fundamental understanding of space, and helps refine long-term mission goals by identifying new objects for other telescopes to observe.

Earth Applications
ASTERIA produces actively stabilized image data from a distributed, low-cost platform. As with Galileo demonstrating how the newly invented telescope could be used to spot pirate ships outside the Venetian Lagoon, ASTERIA’s advances in sensing technology can help reduce risk and support commercial applications. Military satellites or consumer geospatial products, for example, may benefit from these advances.

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Operations

Operational Requirements and Protocols

NanoRacks CubeSats are delivered to the ISS already integrated within a NanoRacks CubeSat Deployer (NRCSD) or NanoRacks DoubleWide Deployer (NRDD). A crew member transfers each NRCSD/NRDD from the cargo vehicle to the Japanese Experiment Module (JEM). Visual inspection for damage to each NRCSD is then performed. When CubeSat deployment operations begin, the NRCSD/NRDDs are unpacked, mounted on the JAXA Multi-Purpose Experiment Platform (MPEP), and placed on the JEM airlock slide table for transfer outside the ISS. A crew member operates the JEM Remote Manipulating System (JRMS) – to grapple and position for deployment. CubeSats are deployed when JAXA ground controllers command a specific NRCSD.
 
ASTERIA is deployed, either individually or in tandem with another CubeSat, then drifts away from the ISS. After a 30-minute waiting period, the solar arrays are deployed and the spacecraft attitude is stabilized. The spacecraft turns to point the solar array toward the sun and charge the battery. The spacecraft is tracked from the ground, and establishes two-way radio communications with the ground station at Morehead State University. After acquisition and initial communication are established, the checkout phase may begin. The spacecraft and its subsystems are tested to verify that they are functional and operating within required performance levels. During the technology demonstration phase, ASTERIA conducts a series of observations to demonstrate high precision pointing and thermal control.
 
For the pointing stability demonstration, the spacecraft is pointed to a star field that contains a target star, and a few guide stars. The payload is a telescope with a focal plane that is mounted to a stage that is adjusted laterally by piezoelectric positioners. Images of the stars are recorded rapidly, the star centroid positions are determined, and then the spacecraft attitude and focal plane position are adjusted to stabilize the target star image centroid on the detector. The pointing stability is demonstrated over 20-minute observations.
 
Pointing repeatability is 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 attitude and focal plane position.
 
During the thermal control demonstration, the temperature of the focal plane is held nearly constant over a series of 20-minute observations. This is accomplished by using heaters on the back of focal plane that provide small temperature adjustments over the duration of the orbit. The thermal control demonstration may occur during the same period as the pointing control demonstration.
 
Photometry capability is demonstrated by recording star images from a series of observations lasting 20-minutes or longer, with images recorded at 20 Hz and co-added at intervals up to one minute. The recorded images are downlinked and analyzed to confirm that they are suitable for generation of a light curve showing normalized brightness of the target star.
 
After completion of the technology demonstration phase, ASTERIA may be used to observe stars for scientific study. The mission duration is planned for 90 days.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Information Pending

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Related Websites
Jet Propulation Laboratory-ASTERIA

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Imagery