The Space Astronomy Group makes researches mainly on the Cosmic Infrared backgrounds from early universe, and Galactic interstellar medium,
based on the various observational data obtained in the space. To do that, the group has succesfully built several space and rocket instruments: FIMS, MIRIS
, CIBER, and NISS. The group takes part in international space telescope projects such as MESSIER, SPHEREx, and WFIRST,
to enhance group’s capability for long term goal of building Korean 1m-class space telescope.
SPHEREx is a NASA MIDEX program for the all-sky spectral survey in the near-infrared (0.75–5 µm) wavelengths. KASI participates the program for 1) calibration of the instruments, 2) development of the observation simulation and the data reduction, and 3) scientific researches.
Thermal and Optical Subsystems of the SPHEREx Spacecraft
The Multi-purpose IR Imaging System (MIRIS)
is the main payload of the third Korean scientific small satellite, STSAT-3.MIRIS
consists of two near-infrared (NIR) cameras,
the Space Observation Camera (SOC) and the Earth Observation Camera (EOC). The SOC is a NIR (0.9–2.0 μm) imaging camera with an aperture of
80 mm and a field of view of 3.67° × 3.67°; it uses a 256 × 256 PICNIC sensor. The telescope part of the SOC will be cooled to 200 K by
radiative cooling to reduce the thermal noise, and the dewar component will be cooled to 80 K to ensure the best performance of the IR sensor.
There are two scientific goals for the SOC: one is to detect the cosmic IR background emission to study its origin and distribution,
and the other is to survey the Pa-α emission line along the Galactic plane to study the warm ionized medium. The dewar contains
a filter wheel and six filters to assist in the completion of these objectives. The SOC flight model was developed, tested,
and calibrated successfully by the end of 2012. STSAT-3 was launched in 2013-11 for its two-year mission.
MIRIS: The SOC Flight Model
Cosmic Infrared Background Experiment 1 (CIBER1) is a rocket-borne instrument designed to study the spectrum, intensity,
and spatial structure of near-infrared (NIR) extragalactic background light.
There are four instruments in CIBER1: I (0.9 μm) and H (1.6 μm) band imagers, a low-resolution spectrometer,
and a narrow-band spectrometer (NBS). CIBER is the term for the ongoing collaboration between Caltech, JPL, and UC Irvine in the US;
Institute of Space and Astronautical Science/ Japan Aerospace Exploration Agency and Nagoya University in Japan; and KASI in Korea.
Cosmic Infrared Background Experiment (CIBER)
There have been three CIBER1 flights thus far, and one additional flight is scheduled. In addition, two flights of the CIBER2 instrument are now planned.
- CIBER1 First Flight: CIBER1 was launched from the White Sands Missile Range in New Mexico,
US on a Terrier-Black Brant sounding rocket on 2009-02-25 at 3:45 AM. The vehicle performed as expected,
and the payload achieved an apogee of 320 km. All flight events went according to plan. CIBER1 observed seven science fields,
including an acquisition of Vega at the end of the flight to check the NBS absolute calibration.
The first flight resulted in the discovery of a silicate absorption feature in the zodiacal light spectrum,
as reported in Tsumura et al. (2010).
- CIBER1 Second Flight: The first flight of CIBER1 uncovered a problem with emission from the hot skin scattering into the optics.
Other than this unanticipated problem, the experiment worked as planned.
The instrument was modified to eliminate the scattered light response by adding a cryogenic pop-up baffle that extends ~10 cm in flight,
eliminating any view of the skin section and vacuum shutter door. The second flight of CIBER1 was on 2010-07-10 at 10:50 PM.
The flight data from the second flight are of high quality, and an analysis for scientific publication is well under way.
- CIBER1 Third Flight: The third flight of the current instrument was launched in 2012.
We used this flight to observe the same fields six months after the second one, at full instrument sensitivity,
during which the line of sight through the zodiacal dust was modulated to test whether the zodiacal foreground is spatially smooth at the required level.
We could also test whether the Fraunhofer line brightness follows seasonal variations in the zodiacal brightness to distinguish
the line emission coming from scattered Galactic starlight.
- CIBER1 Fourth Flight: The fourth flight of CIBER1 was launched on 2013-06-02. CIBER observed in the NIR range,
as the expansion of the universe stretched the original short ultraviolet wavelengths to the long NIR today.
CIBER1 investigated two telltale signatures of the first star formation: the total brightness after all the foregrounds are subtracted and
a distracting pattern of spatial variations. Its measurement is extremely difficult technically.
The KASI Space Astronomy Team is developing a Near-infrared Imaging Spectrometer for Star formation history (NISS),
which will be the main payload of the Korean microsatellite NEXTSat-1. With a large field of view of 2° × 2° and
a linear variable filter with a resolving power of 20, NISS is dedicated to observing the cosmic infrared background and
nearby galaxies to study the star formation history. We plan to use a HgCdTe detector with a wavelength coverage of 0.95–2.5 µm operating at 80 K. This is the conceptual design of the NISS and the detector system, which was launched onboard NEXTSat-1 in 2018.
Engineering and qualification models of NEXTSat-1 (left) and NISS (right)