High Altitude Optical Aeronomy Observatory
Located at Indian Astronomical Observatory, Hanle, Leh Ladakh, India
Located at Indian Astronomical Observatory, Hanle, Leh Ladakh, India
A multi-wavelength allsky airglow imager has been installed over the Indian Himalayan region at Hanle, Leh Ladakh, (32.77°N, 78.97°E; Magnetic dip latitude ~24.1°). This is the first of its kind that is installed in the Indian Himalayan region at an altitude of around 4200 m above the mean sea level. The allsky imager is located at the base camp of the Indian Astronomical Observatory which is operated by Indian Institute of Astrophysics, Bengaluru, India. The imager was procured through an extramural research grant from the Science and Engineering Research Board, Department of Science and Technology, Government of India.
The allsky imaging system purchased from Keo Scientific Ltd., Canada consists of mainly two parts: an optical system and a detector. The optical part contains f/4 Mamiya fish-eye lens with a focal length 24 mm in the front end of the imager with a maximum field of view 180°. However, we have kept the imager with an effective field of view of ~140° to remove the mountain area at the low elevation angle. The imager also contains a shutter which protects the high sensitive CCD camera of the imager from daylight. The imager and its data acquisition system are kept inside a weatherproof PUF container for the protection against the harsh winter at Hanle, Leh Ladakh especially during winter season. The imager is mounted vertically and looks into the sky through a 10-inch hole on the roof of the container. It is covered with a BK7 glass dome which has SiO2 and BBAR anti-reflective coating to protect the primary lens of the imager from UV rays. It uses 3-inch tele-centric arrangement (Plano-Convex lens pair) to parallel the image rays to the axis of filter wheel before impinging on temperature controlled filter wheel which consists of six slots for mounting interference filters. In this imager, only three slots are in operational state until now. Two slots are mounted with 630.0 and 557.7 nm interference filters with 2 nm bandwidth and another is kept open to observe cloud condition of the sky. The rear-end optics consists of a high sensitive thermoelectrically cooled monochromatic CCD (Atik 4000) that has been installed to detect the image. The CCD has a peak quantum efficiency of 65% at 540 nm wavelength and has 511 × 511 pixel resolution. The optimum exposure time of 180 seconds has been chosen for both 557.7 and 630.0 nm filters during the imaging observation. The imaging system is also capable of taking dark exposure for individual filters in every hour of an observing night. It runs automatically during moonless nights controlled by a customized software and the raw images are systematically stored in the data acquisition system.
The allsky imaging system purchased from Keo Scientific Ltd., Canada consists of mainly two parts: an optical system and a detector. The optical part contains f/4 Mamiya fish-eye lens with a focal length 24 mm in the front end of the imager with a maximum field of view 180°. However, we have kept the imager with an effective field of view of ~140° to remove the mountain area at the low elevation angle. The imager also contains a shutter which protects the high sensitive CCD camera of the imager from daylight. The imager and its data acquisition system are kept inside a weatherproof PUF container for the protection against the harsh winter at Hanle, Leh Ladakh especially during winter season. The imager is mounted vertically and looks into the sky through a 10-inch hole on the roof of the container. It is covered with a BK7 glass dome which has SiO2 and BBAR anti-reflective coating to protect the primary lens of the imager from UV rays. It uses 3-inch tele-centric arrangement (Plano-Convex lens pair) to parallel the image rays to the axis of filter wheel before impinging on temperature controlled filter wheel which consists of six slots for mounting interference filters. In this imager, only three slots are in operational state until now. Two slots are mounted with 630.0 and 557.7 nm interference filters with 2 nm bandwidth and another is kept open to observe cloud condition of the sky. The rear-end optics consists of a high sensitive thermoelectrically cooled monochromatic CCD (Atik 4000) that has been installed to detect the image. The CCD has a peak quantum efficiency of 65% at 540 nm wavelength and has 511 × 511 pixel resolution. The optimum exposure time of 180 seconds has been chosen for both 557.7 and 630.0 nm filters during the imaging observation. The imaging system is also capable of taking dark exposure for individual filters in every hour of an observing night. It runs automatically during moonless nights controlled by a customized software and the raw images are systematically stored in the data acquisition system.