Tomo-e Gozen (Tomo-e) is a wide field optical camera for the Kiso 1.05 m f/3.1 Schmidt telescope operated by
the University of Tokyo. Tomo-e is equipped with 84 chips of front-illuminated CMOS image sensors with a
microlens array. The field of view is about 20 square degrees and maximum frame rate is 2 fps. The CMOS
sensor has 2160x1200 pixels and a size of pixel is 19 microns, which is larger than those of other CMOS sensors.
We have evaluated performances of the CMOS sensors installed in Tomo-e. The readout noise is 2.0 e- in 2 fps
operations when an internal amplifier gain is set to 16. The dark current is 0.5 e-/sec/pix at room temperature, 290K, which is lower than a typical sky background flux in Tomo-e observations, 50 e-/sec/pix. The efficiency
of the camera system peaks at approximately 0.7 in 500 nm.
The Tomo-e Gozen is a wide-field high-speed camera for the Kiso 1.0-m Schmidt telescope, with a field-of-view of 20.7-deg2 covered by 84 chips of 2k x 1k CMOS image sensors with 19-μm pixels. It is capable to take consecutive images at 2-fps in full-frame read with an absolute time accuracy of 0.2 millisecond. The sensors are operated without mechanical coolers owing to a low dark current at room temperature. A low read noise of 2-e- achieves higher sensitivity than that with a CCD sensor in short exposures. Big data of 30-TBytes per night produced in the 2-fps observations is processed in real-time to quickly detect transient events and issue alerts for follow-ups.
The Tomo-e Gozen is an extremely wide-field optical camera for the Kiso 1.0-m Schmidt telescope. It is capable of taking consecutive frames with a field-of-view of 20 deg2 and a sub-second time-resolution, which are achieved by 84 chips of 2k×1k CMOS sensor. This camera adopts unconventional designs including a lightweight structure, a nonvacuumed and naturally-air cooled system, front-side-illuminated CMOS sensors with microlens arrays, a sensor alignment along a spherical focal plane of the telescope, and massive readout electronics. To develop technical components necessary for the Tomo-e Gozen and confirm a feasibility of its basic design, we have developed a prototype-model (PM) of the Tomo-e Gozen prior to the final-model (FM). The Tomo-e PM is equipped with eight chips of the CMOS sensor arranged in a line along the RA direction, covering a sky area of 2.0 deg2. The maximum frame rate is 2 fps. The total data production rate is 80 MByte sec-1 at 2 fps, corresponding to approximately 3 TByte night-1. After laboratory testing, we have successfully obtained consecutive movie data at 2 fps with the Tomo-e PM in the first commissioning run conducted in the end of 2015.
KEYWORDS: Phase modulation, Cameras, CMOS sensors, Data storage, Data processing, Computing systems, Signal detection, Observatories, Data acquisition, Astronomy
The Tomo-e Gozen camera is a next-generation, extremely wide field optical camera, equipped with 84 CMOS sensors. The camera records about a 20 square degree area at 2 Hz, providing “astronomical movie data”. We have developed a prototype of the Tomo-e Gozen camera (hereafter, Tomo-e PM), to evaluate the basic design of the Tomo-e Gozen camera. Tomo-e PM, equipped with 8 CMOS sensors, can capture a 2 square degree area at up to 2 Hz. Each CMOS sensor has about 2.6 M pixels. The data rate of Tomo-e PM is about 80 MB/s, corresponding to about 280 GB/hour. We have developed an operating system and reduction softwares to handle such a large amount of data. Tomo-e PM was mounted on 1.0-m Schmidt Telescope in Kiso Observatory at the University of Tokyo. Experimental observations were carried out in the winter of 2015 and the spring of 2016. The observations and software implementation were successfully completed. The data reduction is now in execution.
ISLE is a near-infrared imager and spectrograph for the Cassegrain focus (f/18) of the 1.88 m telescope at
Okayama Astrophysical Observatory. It is upgraded instrument with a new detector, HAWAII-1 HgCdTe array
and new optics. ISLE provides imaging capabilities which covers 4.2 × 4.2 arcmin2 field-of-view at 0.25 arc-sec/
pixel and long-slit (4 arcmin) spectroscopic capabilities at λ/Δλ = 1000 - 4000 using reflection gratings.
The noise performance of the detector is excellent. The read noise of 2.5 electrons with 25 Fowler pairs has
been achieved, that is one of the world's lowest level among the instruments which use HAWAII-1 array as the
detector. We discuss the technical performance of ISLE and examine the upgrade effectiveness.
ISLE is a near-infrared (1.0-2.5μm) imager and spectrograph for the Cassegrain focus (f/18) of the 1.88 m telescope at Okayama Astrophysical Observatory. The detector is a HAWAII 1024 × 1024 HgCdTe Array, which covers 4.2 × 4.2 arcmin2 field of view with a pixel scale of 0.25 arcsec/pixel. ISLE also provides medium (R=300 - 4800) resolution long-slit (4 arcmin long spectroscopic capabilities using reflection gratings. A dedicated front-end electronics for the detector achieved a readout noise of 8 electrons by the conventional Fowler sampling, and a operation scheme that combined with a number of discarded readout greatly suppressed the reset anomaly. The measured limiting magnitudes were J=18.6 and K=17.7 (imaging of point sources at S/N=10 for 10 min.
exposure).
Air-OPUS is a hyper spectral imaging spectrograph, with 0.34 nm spectral step, 190-455 nm spectral coverage, and 330 spatial channels covering 15 degrees field of view (FOV). It is designed as an airborne instrument for the demonstration of spaceborne-OPUS. After two-demonstration campaign using the Gulfstream-II aircraft, the performances of AIR-OPUS, such as spectral resolution, signal-to-noise ration (SNR) have been evaluated. It is concluded that the performances have agreed with designed value. This paper describes design, the performance, and the first results of Air-OPUS. Concept of next generation Air-OPUS, with wider FOV and visible/near-IR spectral coverage, will be also briefly presented.
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