Monday, September 17, 2012

JAXA Super Sensitive camera : Real time night video from the ISS

I am fascinated by time lapse videos of earth at night shot from the ISS. Several of these videos were made and uploaded on streaming sites in the past months and they precisely depict earth in all its beauty : city lights flybys, dancing auroras and lightings that are striking the dark ground of continents and oceans.

But all of these movies are not based on videos footage. Instead, they were patiently built by artists by stacking thousands of long exposure pictures made by the ISS astronauts using Nikon digital cameras. The Nikon cameras are usually bracket mounted in the ISS cupola to keep a stable framing. An automatic remote control system is then plugged to the camera in order to take continuous long exposure of around 2s during a flyby of earth at night that the ISS will cover in about 40 minutes.
The artists have then to manually stitched the photos (most of time after a despeckling/ denoising operation that will improve the quality of each pics).

The main issue with the use of video camcorder to record at night from the ISS is the same as you will have shooting the sea from a cliff on a moonless night : Very low light condition and no way to use projectors to better render the scene.
But what about building a dedicated video camera that push the sensitivity border enough to film in the dark and make possible to get real time videos of earth at night ?

That is what JAXA the Japanese space agency made with the help of NHK broadcasting company. They built the SS-HDTV, the super sensitive HDTV video camera and flew it to space.

1 : Lens (shown here is a Fujinon HA18x7.6ERM/ERD lens), 2 : Camera body, 3 : LCD screen, 4 : SD card recorder
(credit : JAXA)

The camera was delivered to the ISS by the Progress M-10M on 29 April 2011 and transferred to the Kibo module. It then waited for its operator, the japanese astronaut Satoshi Furukawa who boarded the station in June 2011.
Within the next 2 months, Satoshi prepared and set up the camera. He then transmitted videos during a period that culminated with a four-segment live TV show in September 2011.

Satoshi Furukawa recorded lightning, auroras and the islands of Japan at night with the SS-HDTV
(credit : JAXA/NHK)

The camera is built around a 2/3" EM-CCD sensor, EM stands for Electron multiplyer. This CCD technology is quite new and its main advantage is to deliver a very good signal to noise ratio as well as low light capabilities. Therefore, EM-CCDs cameras find growing use in astronomy and scientific application where light become scarce.
Thanks to its sensor, the SS-HDTV can work with a minimum illumination of 0,05 lux.

Surrounding the sensor is a thoughened body that give protection from the solar radiation level that is higher in the ISS than on ground level. On one side of the body is a liveview LCD monitor, on the other is a SD card reader that records the video sequences on 32GB interchangeable SD cards.
An interchangeable lens is used to focus the image. A set of 5 lenses is available in the ISS :
Four fixed focal lens : 4,8mm, 8mm, 17mm, 25mm and one zoom lens : 7,6 ~ 137mm 16X.

The video sequences are encoded using the MPC (Multi-Protocol Converter) at 27Mbit/s before downlinking it to earth through the Ku-band data flow of the station. The MPC, developped by NASA, ESA and JAXA is used to compress HD video stream and therefore limit the use of bandwidth. This operation is achieved either in real time or by processing

The camera was extinsively used by Satoshi until October 2011. No activity is reported in the ISS status since this time.

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