Astrophysics CubeSat Demonstrates Big Potential in a Small Package

The ASTERIA satellite, which was deployed into low-Earth
orbit
in November, is only slightly larger than a box of cereal, but
it could
be used to help astrophysicists study planets
orbiting other stars.

Mission managers at NASA’s Jet Propulsion Laboratory in
Pasadena, California, recently announced that ASTERIA has
accomplished all of
its primary mission objectives,
demonstrating that the miniaturized
technologies on board can
operate in space as expected. This marks the success
of one of
the world’s first astrophysics CubeSat missions, and shows that
small,
low-cost satellites could be used to assist in future
studies of the universe
beyond the solar system.

“ASTERIA is small but mighty,” said Mission Manager Matthew
W.
Smith of JPL. “Packing the capabilities of a much larger
spacecraft into a
small footprint was a challenge, but in the
end we demonstrated cutting-edge
performance for a system this
size.”

Seeing
Stars

ASTERIA, or the Arcsecond Space Telescope Enabling Research
in
Astrophysics, weighs only 22 pounds (10 kilograms). It carries
a payload for
measuring the brightness of stars, which allows
researchers to monitor nearby
stars for orbiting exoplanets
that cause a brief drop in brightness as they
block the
starlight.

This approach to finding and studying exoplanets is called the
transit method. NASA’s Kepler Space Telescope has detected more
than 2,300
confirmed planets using this method, more than any
other planet-hunting
observatory. The agency’s next
large-scale, space-based planet-hunting observatory, the
Transiting Exoplanet
Survey Satellite (TESS), is anticipated
to discover thousands of exoplanets and
scheduled to launch
from Cape Canaveral Air Force Station in Florida on April
16.

In the future, small satellites like ASTERIA could serve as
a
low-cost method to identify transiting exoplanets orbiting
bright, Sun-like
stars. These small satellites could be used
to look for planetary transits when
larger observatories are
not available, and planets of interest could then be
studied
in more detail by other telescopes. Small satellites like
ASTERIA could
also be used to study certain star systems that
are not within the field of
view of larger observatories, and
most significantly, focus on star systems
that have planets
with long orbits that require long observation campaigns.

The ASTERIA team has now demonstrated that the satellite’s
payload can point directly and steadily at a bright source for
an extended
period of time, a key requirement for performing
the precision photometry
necessary to study exoplanets via the
transit method.

Holding steady on a faraway star is difficult because there
are many things that subtly push and pull on the satellite,
such as Earth’s atmosphere
and magnetic field. ASTERIA’s
payload achieved a pointing stability of 0.5
arcseconds RMS,
which refers to the degree to which the payload wobbles away
from its intended target over a 20-minute observation period.
The pointing
stability was repeated over multiple orbits, with
the stars positioned on the
same pixels on each orbit.

“That’s like being able to hit a quarter with a laser
pointer
from about a mile away,” said Christopher Pong, the attitude
and
pointing control engineer for ASTERIA at JPL. “The laser
beam has to stay
inside the edge of the quarter, and then the
satellite has to be able to hit
that exact same quarter — or
star — over multiple orbits around the Earth. So
what we’ve
accomplished is both stability and repeatability.”

The payload also employed a control system to reduce
“noise”
in the data created by temperature fluctuations in the
satellite,
another major hurdle for an instrument attempting
to carefully monitor stellar
brightness. During observations,
the temperature of the controlled section of
the detector
fluctuates by less than 0.02 Fahrenheit (0.01 Kelvin, or 0.01
degree Celsius).

Small
satellites

ASTERIA is a CubeSat, a type of small satellite consisting
of
“units” that are 10 centimeters cubed, or about 4 inches on
each side.
ASTERIA is the size of six CubeSat units, making it
roughly 10 centimeters by
20 centimeters by 30 centimeters.
With its two solar panels unfolded, the
satellite is about as
long as a skateboard.

The ASTERIA mission utilized commercially available CubeSat
hardware where possible, and is contributing to a general
knowledge of how
those components operate in space.

“We’re continuing to
characterize CubeSat components that
other missions are using or want to use,”
said Amanda Donner,
mission assurance manager for ASTERIA at JPL.

ASTERIA launched to the International Space Station in
August
2017. Having been in space for more than 140 days, the
satellite is operating
on an extended mission through May.

ASTERIA was developed under the Phaeton Program at JPL.
Phaeton provides early-career hires, under the guidance of
experienced mentors,
with the challenges of a flight project.
ASTERIA is a collaboration with the
Massachusetts Institute of
Technology in Cambridge; where Sara Seager is the
principal
investigator.

News Media Contact

Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-1821
Calla.e.cofield@jpl.nasa.gov

2018-072

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