Carried by a balloon the size of a football stadium, ASTHROS will use a cutting-edge telescope to observe wavelengths of light that aren’t visible from the ground.
Work has begun on an ambitious new mission that
will carry a cutting-edge 8.4-foot (2.5-meter) telescope high into the
stratosphere on a balloon. Tentatively planned to launch in December 2023 from
Antarctica, ASTHROS (short for Astrophysics Stratospheric Telescope for High
Spectral Resolution Observations at Submillimeter-wavelengths) will spend about
three weeks drifting on air currents above the icy southern continent and
achieve several firsts along the way.
Managed by NASA’s Jet Propulsion Laboratory, ASTHROS
observes far-infrared light, or light with wavelengths much longer than what is
visible to the human eye. To do that, ASTHROS will need to reach an altitude of
about 130,000 feet (24.6 miles, or 40 kilometers) – roughly four times higher
than commercial airliners fly. Though still well below the boundary of space
(about 62 miles, or 100 kilometers, above Earth’s surface), it will be high
enough to observe light wavelengths blocked by Earth’s atmosphere.
The mission team recently put the finishing
touches on the design for the observatory’s payload, which includes its telescope
(which captures the light), its science instrument, and such subsystems as the
cooling and electronic systems. In early August, engineers at JPL will begin
integration and testing of those subsystems to verify that they perform as
expected.
While balloons might seem like antiquated technology,
they offer NASA unique advantages over ground- or space-based missions. NASA’s Scientific Balloon Program has
been operating for 30 years at Wallops Flight Facility in Virginia. It launches
10 to 15 missions a year from locations around the globe in support of
experiments across all of NASA’s science disciplines, as well as for technology
development and education purposes. Balloon missions don’t only have lower
costs compared to space missions, they also have shorter times between early
planning and deployment, which means they can accept the higher risks
associated with using new or state-of-the-art technologies that haven’t yet
flown in space. These risks may come in the form of unknown technical or
operational challenges that can impact a mission’s science output. By working
through these challenges, balloon missions can set the stage for future
missions to reap the benefits of these new technologies.
“Balloon missions like ASTHROS are higher-risk
than space missions but yield high-rewards at modest cost,” said JPL
engineer Jose Siles, project manager for ASTHROS. “With ASTHROS, we’re
aiming to do astrophysics observations that have never been attempted before.
The mission will pave the way for future space missions by testing new
technologies and providing training for the next generation of engineers and
scientists.”
Infrared
Eyes in the Sky
ASTHROS will carry an instrument to measure the
motion and speed of gas around newly-formed stars. During flight, the mission
will study four main targets, including two star-forming regions in the Milky
Way galaxy. It will also for the first time detect and map the presence of two specific
types of nitrogen ions (atoms that have lost some electrons). These nitrogen
ions can reveal places where winds from massive stars and supernova explosions
have reshaped the gas clouds within these star-forming regions.
In a process known as stellar feedback, such violent
outbursts can, over millions of years, disperse the surrounding material and impede
star formation or halt it altogether. But stellar feedback can also cause
material to clump together, accelerating star formation. Without this process, all
the available gas and dust in galaxies like our own would have coalesced into
stars long ago.
ASTHROS will make the first detailed 3D maps of
the density, speed, and motion of gas in these regions to see how the newborn
giants influence their placental material. By doing so, the team hopes to gain
insight into how stellar feedback works and to provide new information to
refine computer simulations of galaxy evolution.
The Carina Nebula, a star-forming region in the Milky Way galaxy, is among four science targets that scientists plan to observe with the ASTHROS high-altitude balloon mission. ASTHROS will study stellar feedback in this region, the process by which stars influence the formation of more stars in their environment. Image Credit: NASA, ESA, N. Smith (University of California, Berkeley) et al., the Hubble Heritage Team (STScI/AURA)
› Larger view
A third target for ASTHROS will be the galaxy
Messier 83. Observing signs of stellar feedback there will enable the ASTHROS team
to gain deeper insight into its effect on different types of galaxies. “I
think it’s understood that stellar feedback is the main regulator of star formation
throughout the universe’s history,” said JPL scientist Jorge Pineda,
principal investigator of ASTHROS. “Computer simulations of galaxy
evolution still can’t quite replicate the reality that we see out in the
cosmos. The nitrogen mapping that we’ll do with ASTHROS has never been done
before, and it will be exciting to see how that information helps make those
models more accurate.”
Finally, as its fourth target, ASTHROS will
observe TW Hydrae, a young star surrounded by a wide disk of dust and gas where
planets may be forming. With its unique capabilities, ASTHROS will measure the
total mass of this protoplanetary disk and show how this mass is distributed
throughout. These observations could potentially reveal places where the dust
is clumping together to form planets. Learning more about protoplanetary disks
could help astronomers understand how different types of planets form in young
solar systems.
A
Lofty Approach
To do all this, ASTHROS will need a big
balloon: When fully inflated with helium, it will be about 400 feet (150
meters) wide, or about the size of a football stadium. A gondola beneath the
balloon will carry the instrument and the lightweight telescope, which consists
of an 8.4-foot (2.5-meter) dish antenna as well as a series of mirrors, lenses,
and detectors designed and optimized to capture far-infrared light. Thanks to
the dish, ASTHROS tied for the largest telescope to ever fly on a high-altitude
balloon. During flight, scientists will be able to precisely control the
direction that the telescope points and download the data in real-time using
satellite links.
This time-lapse video shows the launch of the Stratospheric Terahertz Observatory II (STO-2), a NASA astrophysics mission, from Antarctica in 2016. Such high-altitude balloon missions provide the opportunity to observe wavelengths of light that are blocked by Earth’s atmosphere. Credit: NASA/JPL-Caltech
› Larger view
Because far-infrared instruments need to be
kept very cold, many missions carry liquid helium to cool them. ASTHROS will
instead rely on a cryocooler, which uses electricity (supplied by ASTHROS’
solar panels) to keep the superconducting detectors close to minus 451.3
degrees Fahrenheit (minus 268.5 degrees Celsius) – a little above absolute
zero, the coldest temperature matter can reach. The cryocooler weighs much less
than the large liquid helium container that ASTHROS would need to keep its
instrument cold for the entire mission. That means the payload is considerably
lighter and the mission’s lifetime is no longer limited by how much liquid
helium is on board.
The team expects the balloon will complete two
or three loops around the South Pole in about 21 to 28 days, carried by
prevailing stratospheric winds. Once the science mission is complete, operators
will send flight termination commands that separate the gondola, which is
connected to a parachute, from the balloon. The parachute returns the gondola
to the ground so that the telescope can be recovered and refurbished to fly
again.
“We will launch ASTHROS to the edge of
space from the most remote and harsh part of our planet,” said Siles.
“If you stop to think about it, it’s really challenging, which makes it so
exciting at the same time.”
A division of Caltech
in Pasadena, JPL manages the ASTHROS mission for the Astrophysics Division of NASA’s
Science Mission Directorate. JPL is also building the mission payload. The Johns
Hopkins Applied Physics Laboratory in Maryland is developing the gondola and
pointing systems. The 2.5-meter antenna unit is being built by Media Lario
S.r.l. in Lecco, Italy. The payload cryocooler was developed by Lockheed Martin
under NASA’s Advanced Cryocooler Technology Development Program. NASA’s Scientific
Balloon Program and its Columbia Science Balloon Facility will provide the
balloon and launch services. ASTHROS is scheduled to launch from McMurdo
Station in Antarctica, which is managed by the National Science Foundation
through the U.S. Antarctic Program. Other key partners include Arizona State
University and the University of Miami.
News Media Contact
Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov
2020-144
Source: Jet Propulsion Laboratory