The NASA Nikon F4 Electronic Still Camera (ESC) was the first digital camera used by NASA aboard the Space Shuttle Orbiters. Design began in 1987 and prototypes were developed over the following years before the finished camera finally made its maiden voyage aboard Shuttle Discovery during STS-48 in 1991.
The camera was built to fill the needs of a variety of customers who longed for a faster way of capturing and transmitting images from the orbiter back to Earth in as close to real-time as possible. Prior to this, camera images were captured on film and the film was processed and printed only after the spacecraft returned to earth, making for long delays in getting images to the Control Center as well as to the media. Principal drivers included Intelsat and The Hubble Space Telescope, along with the media, the science community (most notably Earth Observations) and of course, Mission Control.
The ESC's design was a revolutionary milestone in that for the first time, enabled a camera to electronically capture and digitize an image with resolution approaching film quality (most notably its dynamic range, signal to noise ratio and resolution). The digital image was stored on removable hard disks, and could be converted to a format suitable for downlink transmission or enhanced using image processing software. Although there was talk about using an optical disk system for storage, that never transpired. The ability to enhance and annotate high-resolution images on orbit and downlink them in real-time would improve the astronauts' photo-documentation capabilities of Earth observations and on-board activity on the Space Shuttle.
Initially, the first prototype for a digital solution was built with a Nikon F3 camera as the base. The prototype was developed in NASA's lab and was a collosal assortment of wire wrap circuit boards and cables as the technicians were trying to make a proof of concept. Once the details of the internal design could be fine tuned, a finished 'housing' for the handheld digital camera could be developed. With Nikon busy developing the autofocus F4 and the then current state of the F3 prototype it soon became clear that the Administration should partner with Nikon's newest professional body to bring the ESC to fruition.
The ESC employed a Nikon F4 body as the foundation for the image capture. The F4 was kept very close to the consumer version in form and function, enabling the same shooting modes and the capability to mount & control the same lenses. The key change was that Nikon needed to modify the electronics to allow signal exchanges between the F4 body and the NASA-built electronics for exposure control; the point where integration between the digital back and the camera starts and ends. NASA was responsible for developing the ESC's electronics, firmware, software, mechanical housings and ground systems; each of which were developed by a team at NASA's Johnson Space Center
The sensor in the ESC was a Ford Aerospace FA1024L which was developed by JPL and Ford Aerospace as a part of the Hubble Space Telescope sensor development program. The sensor was a 1024 x 1024 (1 million picture element (pixel)) charge coupled device (CCD) positioned at the film plane, and recorded images in monochrome with 8 bits of digital information per pixel (256 gray levels).
Although modern digital Nikons utilize a sensor proportional to that of 35mm film (24mm x 36mm), the NASA chose a square sensor for the F4 ESC measuring 15mm x 15mm. According to the design team, the square format was chosen because square pixels are preferred for image processing purposes. In addition, calculations are easier if the pixels are arranged in a square matrix. Spatial filters work correctly, distance measurements from one point to another are easier, etc. The smaller sensor size also ensured that the lenses did not need further modification and that the images captured would not have vignetting.
Once the image was captured by the sensor, it was then stored on a removable computer hard disk which was produced by a Colorado based company called PrairieTek.
The hard drive was stored inside the NASA designed and manufactured Electronics Box Assembly. This box was the control system for the images. The unit enabled 4 different modes for managing the images:
Mode 1 would record images captured by the sensor, directly to the hard drive
Mode 2 would record images and simultaneously downlink them to an onboard IBM Thinkpad laptop
Mode 3 would solely downlink images from the hard drive to the laptop
Mode 4 would trigger the recording of the images by way of a self timer, then captured those images on the sensor and write them directly to the hard drive
The images could be viewed and enhanced on board using a modified GRID lap-top computer (aka PDU or Playback Downlink Unit) before being transmitted to the ground via the orbiter digital downlinks. This unit was referred to as 'Gridcase'
Aside from the internal electronics changes and the replacement of the film plane with the Digital back, the F4 was very close to the commercial version, with a few other modifications.
The NASA Nikon F4 ESC only had up to 1/2000 shutter speed, compared to the commercial version's 1/8000 second.
I have been unable to ascertain why the two high speeds of the commercial version did not appear on the NASA F4 ESC. One possible reason was that since NASA was working with Nikon on the ESC long before the commercial release of the F4, the earliest version of the camera perhaps did not have those two high shutter speeds, however the 'space' on the shutter speed dial seems to imply that they were planning on 1/4000 & 1/8000. Another possible reason is that given the available light in space, its unlikely that fast of a shutter speed would ever be used.
The F4 body was also fitted with a DA-20 AE Action Finder and an eyepiece hood to enable enough extension over the digital back, since the back extended roughly 4 cm from the body
A number of other body modifications were observed including:
- To accommodate the size and square format of the CCD sensor, the internal film rails were milled out on the top and bottom, approximately 30mm
- The internal film rails are flat black and not polished; to avoid any reflected light from imapacting the image on the sensor
- The film roller normally located to the left of the aperture, is not installed
- The film sensing lever by the sprocket assembly is also not installed
- The focusing screen area has an app.15mm square mask installed to accommodate the square format sensor
- The effective ASA / ISO range for the NASA F4 ESC was ISO 200 with visible light only and ISO 400 when using both visible light and near infrared.
The debut of the ESC during STS-48 proved to be a great success as images were captured both inside the Shuttle and through the Shuttle observation windows. The external images were especially important for not only capturing images of Earth, but for repair and servicing images for Hubble, Intelsat, the Upper Atmospheric Research Satellite and a host of others. Those images were then successfully downlinked from the Shuttle to Mission Control at the Johnson Space Center (JSC) where they were processed on a workstation and then stored on disks for transfer to JSC's Electronic Still Camera Laboratory. There, the images were processed on a PIXAR imaging computer and printed with a 3M Color Laser Imager, an advanced 300 dpi color output device that was capable of printing over 170 photographic quality originals an hour. The initial goal was to have hard-copy images within 1 hour after the image was received in Mission Control.
The success of the project and seeing the system's tremendous potential, the ESC was selected by the Pentagon to become the core for NASA's HERCULES project: The Hand-held Earth-oriented Real-time Cooperative, User-friendly, Location, targeting, and Environmental System.
The ESC would eventually fly on 8 Shuttle missions including STS-44, STS-45, STS-42, STS-49, STS-53, STS-56 and finally STS-61 in late 1993.
From my research, I have learned that at least 14 modified F4 bodies were produced by Nikon for NASA's Electronic Still Camera project. In total, only three NASA F4 Electronic Still Cameras were eventually produced (internally referred to as Huey, Dewey & Louie. Although the NASA development team, along with Ford Aerospace & JPL, had developed a 2048 x 2048 CCD Sensor to upgrade the ESC, as well as alternate architecture CCDs and a Colour CCD, the project was shelved in favour of the Kodak DCS460 cameras which would take NASA to the next level in DSLR photography.
The development team at NASA would be disbanded and the remaining staff's role would change to certifying the flight readiness of future digital cameras