Lunar Orbiter 4

Lunar Orbiter 4

Image purported to have been taken by Lunar Orbiter 4, showing the Moon with a crescent Earth in the background. This image may be either fake or mis-attributed. Enhanced by LOIRP.
Mission type	Lunar orbiter
Operator	NASA
COSPAR ID	1967-041A
SATCAT №	2772
Mission duration	180 days
Spacecraft properties
Manufacturer	Langley Research Center
Launch mass	385.6 kilograms (850 lb)
Start of mission
Launch date	May 4, 1967, 22:25:00 (1967-05-04UTC22:25Z) UTC
Rocket	Atlas SLV-3 Agena-D
Launch site	Cape Canaveral LC-13
End of mission
Last contact	July 17, 1967 (1967-07-18)
Decay date	October 6, 1967
Orbital parameters
Reference system	Selenocentric
Semi-major axis	6,152.5 kilometers (3,823.0 mi)
Eccentricity	0.28
Periselene	4,449 kilometers (2,764 mi)
Aposelene	7,856 kilometers (4,881 mi)
Inclination	85.5 degrees
Period	721 minutes
Epoch	7 March 1967, 20:00:00 UTC
Lunar orbiter
Orbital insertion	May 8, 1967, 21:54 UTC
Orbits	360
---- Lunar Orbiter program ← Lunar Orbiter 3 Lunar Orbiter 5 →

Lunar Orbiter 4 was an unmanned U.S. spacecraft, part of the Lunar Orbiter Program, designed to orbit the Moon, after the three previous orbiters had completed the required needs for Apollo mapping and site selection. It was given a more general objective, to "perform a broad systematic photographic survey of lunar surface features in order to increase the scientific knowledge of their nature, origin, and processes, and to serve as a basis for selecting sites for more detailed scientific study by subsequent orbital and landing 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 near polar high lunar orbit for data acquisition. The orbit was 2,706 by 6,111 kilometres (1,681 mi × 3,797 mi) with an inclination of 85.5 degrees and a period of 12 hours.

After initial photography on May 11, 1967 problems started occurring with the camera's thermal door, which was not responding well to commands to open and close. Fear that the door could become stuck in the closed position covering the camera lenses led to a decision to leave the door open. This required extra attitude control maneuvers on each orbit to prevent light leakage into the camera which would ruin the film. On May 13 it was discovered that light leakage was damaging some of the film, and the door was tested and partially closed. Some fogging of the lens was then suspected due to condensation resulting from the lower temperatures. Changes in the attitude raised the temperature of the camera and generally eliminated the fogging. Continuing problems with the readout drive mechanism starting and stopping beginning on May 20 resulted in a decision to terminate the photographic portion of the mission on May 26. Despite problems with the readout drive the entire film was read and transmitted. The spacecraft acquired photographic data from May 11 to 26, 1967, and readout occurred through June 1, 1967. The orbit was then lowered to gather orbital data for the upcoming Lunar Orbiter 5 mission. The spacecraft was used for tracking until it struck the lunar surface due to the natural decay of the orbit no later than October 31, 1967, between 22–30 degrees W longitude.

Notable accomplishments

Lunar Orbiter IV provided photographs containing an enormous amount of data and scientific information about the nearside of the Moon. It was the first such mapping of the Moon.

Significant accomplishments of the mission include:

• Provided the first photographic mapping mission of a celestial body, other than Earth, from an orbiting spacecraft.
• Provided photographic coverage (over 99%) of the nearside of the Moon at resolutions at least 10 times better than Earth-based observations.
• Provided the first detailed near-vertical photographs and visibility of the polar regions and limb areas. These areas can only be seen at an oblique angle from Earth.

Photographs

Spacecraft orbit and photographic coverage on the near side (left) and far side (right)

The film was developed on board using a then-classified BIMAT process. https://www.nationalgeographic.com/science/2019/02/moon-photographs-from-1960s-were-developed-in-space-heres-how Internal document from 1966, declassified in 2001 https://www.cia.gov/library/readingroom/docs/CIA-RDP33-02415A000500120032-7.pdf "The continuous processing method with the rapid-access availability of a positive image is especially suited to cathode ray tube monitoring." The cameras were also from recon.

There are major discrepancies in the reported number of photographs returned by Lunar Orbiter 4, as well as for the entire Lunar Orbiter program. Reported numbers for the series of 5 orbiters range from 1654 to 2180, and up to 2600. According to the Wikipedia page for Lunar Orbiter 4,

a total of 419 high-resolution and 127 medium-resolution frames were acquired, covering 99% of the Moon's near side at resolutions from 58 to 134 metres (190 to 440 ft).

Nasa's 1970 Guide to Lunar Orbiter Photographs

In 1970, NASA published its Guide to Lunar Orbiter Photographs. During the conversion process from magnetic tape to film, the video signal was intentionally distorted.

P1. "The five Lunar Orbiter spacecraft returned over 1654 [pictures]" Up to 426 pitures each. 426 * 5 = 2130. 2130 - 1654 = 476

P6."h-resolution frames.The negative images on the spacecraft film were readout in parts, termed "framelets", and reconstructed on Earth on 35-mm film as positive images of the Moon at a scale (GRE scale) 7.18 × spacecraft scale. The framelets were then used to make reassembled frames in various forms.

20- BY 24-INCH SECTIONS

The framelets reconstructed in the GRE represent the original flight data and are designated as zero-generation positives. The original framelets (or copies) were reassembled and contact printed on to 20- by 24-inch sheet film.

the video signal was intentionally distorted prior to input to the GRE

P8. Table. Number of pictures of the Earth for all five Lunar Orbiters- 3 Exposures, 3 useful high resolution, 3 useful low resolution. None are listed for Lunar Orbiter 4.

Mission totals for all lunar Orbiters:

• 1012 Exposures. (Each exposure has one each High and Medium resolution picture.)
• 898 Medium Resolution Complete Frames Useful for Interpretation.
• 695 High Resolution Complete Frames Useful for Interpretation.

Pictures for Lunar Orbiter IV called out in the table:

• 165 exposures, general interest; near side.
• 7 exposures, General interest; far side.

165 + 7 = 172. 2 * 172 = 344 total pictures, usable or otherwise.

WIkipedia: 419 + 127 = 546 total pictures. All of the table entries have high and medium-resolution numbers which are similar to each other, which makes sense because both pictures are on the same section of film and exposed at or about the same time.

1968 Lunar Orbiter IV Photographic Mission Summary

The NASA Contractor Report: Lunar Orbiter IV Photographic Mission Summary (NASA CR-1054), June 1968, list at least two different numbers for the total exposures

On Page 50,

...and, with few exceptions, each of the over 200 photo exposures required individual two- or three-axis spacecraft maneuvers.

On Page 63,

"A total of 398 telephoto and wide-angle photographs (199 dual exposures) was taken during this broad systematic lunar mapping mission essentially as planned. Seventeen of these photos were not developed because "Bimat cut" was commanded earlier than planned.

"Bimat cut" terminated the onboard film development process, rendering the picture unusable. This was done on this particular mission because the motorized "thermal door", essentially a lens cover, was malfunctioning. They decided to leave it open, which caused problems with fogging and stray light. 199 exposures less the 17 undeveloped exposures leaves a total of 182 processed exposures that could then be converted to a video signal and transmitted back to Earth. Each exposures has two pictures (telephoto and wide angle, or high resolution and medium resolution), for a maximum possible of 364 usable pictures.

On Page 65, the report also notes a curious property of the Moon which caused some problems with the photography-

The Moon has unique reflectance characteristics unlike any encountered in terrestrial photography. The wide range of reflectance can and did produce photographic images in adjacent areas having a density range that exceeded the capability of the spacecraft readout system (thus obliterating detail in areas of density extremes) while exhibiting excellent detail in the surrounding areas. Experience gained during previous missions was used to refine the selection of photographic parameters needed to determine the required exposure settings

On Page 67,

One hundred and ninety-two exposures were taken and processed during the mission as follows:

• Nearside perilune 158 frames
• Nearside apolune 7 frames
• Farside apolune 9 frames
• Film set (blank) 18 frames

Working paper CR-66735-1

This working paper presents a compilation of selected Lunar Orbiter photo support data extracted from computer magnetic tapes which were produced by The Boeing Company under the National Aeronautics and Space Administration Contract Number NASA CR-66735-1 through 5. These tapes were processed through the Computation and Analysis division of the Manned Spacecraft Center, Huston and provided by the National Space Science Data Center, Goddard, Persons in and associated with the Mapping Science Laboratory have been hindered in locating the more commonly required photo parameters due to the magnitude and scope of the documents produced by Boeing under the above contract. Formatting of these specific photo parameters in a more concise manner became desirable. This report was prepared by the Lockheed Electronics Company, Huston Aerospace Systems Division, under contract NAS 9-10951, Action Document number 63-2956-1024-29-3, "Lunar Orbiter Catalog" issued by the Mapping Sciences Laboratory, Manned Spacecraft Center, Huston, Texas.

P2.

In producing this catalog, the author has noted some data on the magnetic tape which obviously are erroneous...since some less obvious data errors may exist, no guarantee of data accuracy should be implied.

Instruments and data

Accurate data was acquired from all other experiments throughout the mission. Radiation data showed increased dosages due to solar particle events (a solar flare) producing low energy protons.

Instruments

Lunar Photographic Studies :	Evaluation of Apollo and Surveyor landing sites
Meteoroid Detectors :	Detection of micrometeoroids in the lunar environment
Caesium Iodide Dosimeters :	Radiation environment en route to and near the Moon
Selenodesy :	Gravitational field and physical properties of the Moon

Lunar Orbiter IV continued to provide lunar tracking data to augment the data obtained on the first three missions. The orbit parameters of the 85-degree inclination with relatively high apolune and perilune altitude provided new data for defining the lunar model coefficients and, in particular, data on the Moon’s oblateness. At the end of the photo mission June 1, over 783 station hours of Doppler tracking data had been recorded. Over 79 hours of ranging data and 15 station time correlation checks were also obtained. This data was used to refine the geometric and gravitational mathematical models of the Moon.

See also

• Lunar Orbiter Image Recovery Project
• Exploration of the Moon
• Lunar Orbiter 1
• Lunar Orbiter 2
• Lunar Orbiter 3
• Lunar Orbiter 5

External links

• DESTINATION MOON: A history of the Lunar Orbiter Program (html version) 1976
• Lunar Orbiter Photo Gallery - Mission 4 at the Lunar and Planetary Institute