In various threads about videos and cine footage from shuttle missions there's been a lot of misinformation and confusion about what wavelengths the
most commonly-downlinked TV images are made in -- 'ultraviolet', visible light, IR, some combination. My own records always indicated the images
were centered on visible light and the 'ultraviolet' claims were spurious. I have obtained more detailed technical data from the Johnson Space
Center and will post it here for discussion.
There is also a set of pdf files, referenced in the report below, that are hosted as follows:
Orbiter xmission curves
EMU Helmet-EVVA Specs
• The windows have anti-reflective coatings on them (called HEA). It is a typical vapor deposited Magnesium Flouride compound. The primary
pressure pane also has a "red reflector" coating on it (I do not know the composition).
• None have UV coatings. UV is blocked by the pressure pane substrate (aluminosilicate glass), and for the egress hatch, it is blocked by a
polycarbonate filter which is installed after post-insertion (the egress hatch window does not use aluminosilicate glass).
• The answer about the optical window is this: The orbiters can be configured with a high optical quality window in the ingress/egress
hatch. Because the glass for these windows is expensive, we like to fly the "normal" quality glass here and install the optical quality only when a
request is made.
Shuttle CCTV payload bay cameras
STS-1 vintage cameras - these flew thru STS-88. However, we are flying one with an MLA (monochrome lens assembly) on STS-125 mounted on the
Hubble FSS (Flight Support Station) to view a target that is on the Hubble Telescope to assist in berthing and unberthing.
As a matter of interest, the camera we are flying on STS-125 also flew as one of the cabin cameras on STS-1.
This camera has an intensified vacuum-tube image sensor (called a SIT – silicon intensified target – tube) that is basically black-and-white.
Color was achieved by rotating a color filter wheel at the 60 Hz field rate in front of the image sensor. The resulting filtered video was
reconstructed on the ground by a field-sequential color converter.
The wavelength sensitivity of the SIT tube is shown in the curve in the attached file “TVC”. Also included are the curves for the red, blue and
green filters in the color filter wheel.
CTVC – Color solid-state TV camera – this is the current NTSC color camera which began to fly on STS-61. It has three CCD (charge coupled
device) image sensors, one each for the red, blue and green video channels. The CTVC spectral response is required to exhibit a response
approximating the human eye’s response such that both IR and UV illuminated objects do not appear as “false brightness levels” on a display. A
curve of the eye’s response is included in the attached file “ITVC”.
ITVC – Intensified Black-and-white solid state TV camera – this is the current low-light-level B&W camera which began to fly on STS-78. It
has an intensifier fiber-optically coupled to the same CCD that the CTVC employs which makes the camera low-light level sensitive. The wavelength
sensitivity of the ITVC is shown in the curve in the attached file “ITVC”. You will notice that it’s quite sensitive in the near IR range
making the LDRI (Laser Dynamic Range Imager) laser used on the OBSS (Orbiter Boom Sensor System) which operates in the near IR range a good
illuminator for the ITVC when used as part of the OBSS Sensor Package 1.
Source: Herring, Kyle J. (JSC-AP311)
Sent: Monday, April 20, 2009 11:05 AM
[edit on 21-4-2009 by JimOberg]
[edit on 21-4-2009 by JimOberg]