[FPSPACE] Soviet stamp of Luna 3 with lunar farside image

DwayneDay zirconic1 at earthlink.net
Mon Oct 11 14:00:21 EDT 2004

-----Original Message-----
From: Paolo Ulivi <paolo.ulivi at tiscali.it>
Sent: Oct 11, 2004 1:26 AM

>I think that the main problem was that the Soviets were not able to 
produce "radiation hardened" film at the time, while Genetrix ballons 
probably used such film to avoid it being fogged by cosmic rays in the 
upper atmosphere.


When NASA was selecting a contractor to build Lunar Orbiter they ran into a similar concern.

Several of the contractor proposals used "high speed film," which meant that it only had to be exposed for a very short time (the high speed refers to the amount of time required to put the image to the film).  Some of these used that film because they were spin-stabilized and the camera would sweep over the target really quickly, so the film had to take the exposure during that very short time.

The problem with high speed film is that it is susceptible to fogging from radiation.  This is not a subject that was well understood until very late in the contractor selection (around October 1963).  Some studies indicated that unless there was substantial radiation shielding, this would be a problem.

Fortunately for Boeing, they had selected an Eastman Kodak camera that used lower speed film, equivalent to an ASA rating of 1.6 (if you still use a film camera, most film is rated at 100, 200 or 400 ASA--and as you know, you use 100 speed film when it is very bright out and you can use a short exposure because there is so much light).

One big benefit of low speed film is that the grain is really fine.  This is why it is excellent for reconnaissance cameras, because you can enlarge it a lot.  That is why low speed film was used on the Genetrix balloons and later CORONA missions.

So Kodak had a low speed film camera for Lunar Orbiter and this was naturally resistant to radiation out in lunar orbit.  NASA already wanted to select the Boeing proposal because it was technically excellent, but the film speed sealed the case.


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