Lunar Orbiter 1
Courtesy of NASA's National Space Science Data Center
Launch Date: 1966-08-10
On-orbit dry mass: 385.60 kg (850 lb.)
The Lunar Orbiter 1 spacecraft was designed primarily to photograph smooth
areas of the lunar surface for selection and verification of safe landing
sites for the Surveyor and Apollo missions. It was also equipped to
collect selenodetic, radiation intensity, and micrometeoroid impact data.
The spacecraft was placed in a cislunar trajectory and injected into an
elliptical lunar orbit for data acquisition. It was stabilized in a
three-axis orientation by using the sun and the star Canopus as primary
angular references. A three-axis inertial system provided stabilization
during maneuvers and when the sun and Canopus were occulted by the Moon.
Communications were maintained by an S-band system which utilized a
directional and an omnidirectional antenna. The spacecraft acquired
photographic data from August 18 to 29, 1966, and readout occurred through
September 14, 1966. Accurate data were acquired from all other experiments
throughout the mission. The spacecraft was tracked until it impacted the
lunar surface on command at 7 degrees N latitude, 161 degrees E longitude
(selenographic coordinates) on October 29, 1966.
Lunar Photographic Studies
This experiment consisted of a dual-lens camera system designed to
satisfy the primary mission objective of providing photographic
information for the evaluation of Apollo and Surveyor landing sites.
An 80-millimeter lens system was used to obtain Medium-Resolution (MR) photos,
and a 610-millimeter lens system was used for High-Resolution (HR) photos. The
two separate lens, shutter, and platen systems utilized the same film
supply and recorded imagery simultaneously in adjacent areas of 70-millimeter
film. Automatic sequences of 1, 4, 8, or 16 photos were obtained. At
an altitude of 46 kilometers (29 miles), which was approximately the perilune height, the
HR system photographed a 4.15- by 16.6-kilometer (2.58- by 10.32-mile) area of the lunar surface
which was centered on a 31.6- by 37.4-kilometer (19.64- by 23.2-mile) area photographed by the MR
system. At apolune, which occured on the farside at about 1850-kilometer (1,143-mile) altitude, the areas photographed were correspondingly larger. The film
was bimat processed on board and optically scanned, and the resulting
video signal was telemetered to ground stations. Film density readout
was accomplished by a high-intensity light beam focused to a
6.4-micron-diameter spot on the spacecraft film. The spot scanner
swept 2.67 millimeters in the long dimension of the spacecraft film. This
process was repeated 286 times for each millimeter of film scanned.
The raster was composed of 2.67- by 65-millimeter scan lines along the film.
The video signal received at the ground station was recorded on
magnetic tape and also fed to Ground Reconstruction Equipment (GRE),
which reproduced the portion of the image contained in one raster on a
35-millimeter film positive framelet. Over 26 framelets were required for a
complete MR photograph and 86 for a complete HR image. Of the 211
simultaneous exposures obtained, 206 MR photos and 13 HR photos were
considered usable. A shutter malfunction prevented normal exposure of
most of the HR imagery. Eight each of the usable MR and HR photos are
of the lunar farside, and two of these include the earth's image.
Except of the shutter malfunction, experiment performance was nominal
until the final readout on September 14, 1966. A detailed description
of the experiment, a bibliography, and indexes of all the available
Lunar Orbiter 1 through 5 photos are contained in the report 'Lunar
Orbiter Photographic Data,' NSSDC 69-05, June 1969.
The instrumentation for this experiment included a power source, an
omnidirectional antenna, and a transponder to obtain information for
determining the gravitational field and physical properties of the moon.
High-frequency radio signals were received by the spacecraft from earth
tracking stations and retransmitted to the stations to provide doppler
frequency measurements (range rate) and signal propagation times (range).
The telemetry data were processed in real time on an IBM 7044 computer
in conjunction with an IBM 7094 computer. They were then displayed on
100-wpm teletype machines, x-y plotters, and bulk printers for analysis.
Data coverage was continuous while the spacecraft was visible from the
earth. Information was acquired during the cislunar, the first, second, and
third ellipse, and the extended mission (from end of the photographic
mission to lunar impact) phases of the mission. Doppler, ranging, hour
angle points, and declination angle points data were accumulated during
tracking. The quality of recorded data ranged from good to excellent.
The Lunar Orbiter 1 spacecraft carried 20 micrometeoroid detectors,
located on the tank deck periphery, for the detection of micrometeoroids
in the lunar environment. These half-cylinder-shaped detectors were
pressurized with helium gas. A rupture of the shell by a micrometeoroid
released the gas pressure, thus activating a microswitch that provided the
input signal to the telemetry system. The thickness of the detector walls
was .00127 centimeters.
Cesium Iodide Dosimeters
The principle purpose of the Lunar Orbiter radiation measuring systems
was to monitor, in real time, particle fluxes that would damage processed
film in case of major solar cosmic-ray events. This would make it
possible for the mission control to minimize darkening of the film by
operational maneuvers. A secondary purpose was to acquire a maximum
amount of information on radiations on the way to the moon and near the
moon. The sensor system consisted of two separately monitored thin
cesium iodide scintillators (2-pi solid angle acceptance) that were
positioned and shielded in the same way as the film in the cassette in the
loopers. The shielding thickness of the cassette and cassette dosimeter
was 2 square centimeters sm aluminum. The shielding of the loopers and the looper
dosimeter was 0.17 gm/sq centimeters aluminum. These shielding thicknesses also
corresponded approximately to the thickness of the Apollo module wall
and of a space suit. In the case of protons at verticle incidence, particles
with energy greater than 40 and 11 MeV penetrated 2 and 0.17 gm/sq centimeters,
Lunar Orbiter 2
Views of the Solar System Copyright © 1997 by
Calvin J. Hamilton. All rights reserved.