The Aspera mission is an extreme UV (EUV) astrophysics
small satellite telescope designed to map the warm-hot phase coronal gas around
nearby galaxy halos. Aspera will search for faint and diffuse OVI line
emission using a suite of four spectrographs based on a similar in design to the
successful FUSE mission.
Aspera is funded through the inaugural 2020 NASA Astrophysics Pioneers program
for small missions and has an anticipated launch date
in late 2024. The SmallSat configuration will rideshare to a low Earth Sun-synchronous
orbit. The satellite is 335.6 x 254.0 x 395.29 mm in size and has a ~24 kg mass.
The optical coatings will degrade in the space environment and thus set
a limit on mission operations: performance would be degraded by about 7% after nine
months of operation.
The 103.2,103.6 nm OVI doublet line emission is extremely faint and
distributed over very wide angular areas and thus very challenging to observe with
current and recent past space-based UV instruments. Aspera is fine-tuned to observe
this diffuse faint spectra.
Mission Characteristics
Lifetime : Nine months from launch (projected late 2024)
Energy Range : 11.92–12.03 eV (103.0–104.0 nm)
Special Features : Spectrographs with coated optics to reflect EUV light
and gratings to study a very narrow spectral band around the 103.2,103.6 nm
OVI line.
Payload :
- Spectrograph. The sole observational instrument is a suite of four
modified Rowland-Circle spectrographs with parallel channels. Each is equipped
with a 6.2 cm x 3.7 cm off-axis parabolic mirror and a toroidal diffraction grating,
a flight-proven variant similar to that used in FUSE, but with a
lower spectral resolution in order to make it more sensitive to diffuse sources.
The optical surfaces uses Al+LiF coatings. The detectors are micro-channel plates.
Each of the four spectrographs are offset from each other by 60′ along the
slit width direction.
- Effective area : 1.85 cm2 at 103.5 nm (11.98 eV)
- Angular resolution : < 60 arcsec
- Field of View : 60 arcmin x 30 arcsec
- Focal length : 171.2 mm
- Spectral Resolution: < 0.07 nm at 103.5 nm (λ/δλ >1500)
Science Highlights:
- Map and characterize circumgalactic medium
