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.
The Kyoto Tridimensional Spectrograph II (Kyoto 3DII) is an optical integral field spectrograph mounted on the Subaru telescope as a PI-type instrument. Used with AO188, Kyoto 3DII provides us unique opportunities of optical Integral Field Spectroscopy (IFS) with adaptive optics (AO). While AO works better in redder wavelength regions, quantum efficiency of the previous CCD was low there with optimization for a wider wavelength coverage. To optimize Kyoto 3DII to AO observations, we have newly installed the red-sensitive Hamamatsu fully depleted CCD, which enhances the system efficiency by a factor of ~2 in the red wavelength range. Fringes are dramatically reduced, and the readout noise drops to 3:2-3:4e- about two times smaller than previous, due to refrigerator and readout system. With these improvements, we carried out engineering and scientific observations in September 2015, February and March 2016. We measured the system efficiency using a standard star, and confirmed the successful improvement of the system efficiency. We observed galactic nuclei of nearby galaxies in the Natural Guide Star (NGS) and the Laser Guide Star (LGS) modes. We found the spatial resolution of ~0.1′′ FWHM using a 9.5-magnitude NGS, and ~0.2 - 0:4′′ in LGS mode. Together with the AO resolution, improved efficiency opens a new window for Kyoto 3DII to carry out high resolution optical IFS targeting faint objects such as high-redshift galaxies as well as faint lines such as [OI] λ6300° A and absorption lines of nearby objects.
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.
LISS (Line Imager and Slit Spectrograph) is an imager and spectrograph equipped with a liquid crystal etalon and a low resolution grism. It is specialized to observe and map the emission and absorption lines of astronomical objects. A fully depleted and back illuminated 2K x 1K Hamamatsu CCD which has high sensitivity at redder wavelengths in optical bands enables this instrument to give a good performance in imaging and spectroscopic observations of emission lines such as [SIII]λλ 906.9/953.2 nm. We successfully carried out commissioning observations at the 1.6-m Pirka telescope of Hokkaido University in September/October 2012 and June/July 2013. In this paper, we describe the design and performance of LISS as well as its early observational results and future prospects.