PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "20090626, L. Gaddis - Initial Version, 20101001, C. Isbell - Post Review" RECORD_TYPE = STREAM OBJECT = MISSION MISSION_NAME = "LUNAR ORBITER IV" OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = "LO4" OBJECT = MISSION_TARGET TARGET_NAME = MOON END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_INFORMATION MISSION_START_DATE = 1967-05-04 MISSION_STOP_DATE = 1967-10-31 MISSION_ALIAS_NAME = "LO4" MISSION_OBJECTIVES_SUMMARY = "As described in MISSION_DESC below." MISSION_DESC = " THE LUNAR ORBITER IV MISSION ============================ Overview -------- Much of the information in this document was abstracted from the Lunar Orbiter mission pages of the National Space Science Data Center (NSSDC) Web site (http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1967-041A). See references cited for more detail. The Lunar Orbiter IV mission had the general objective to perform a broad photographic survey of lunar surface to increase knowledge of their form and distribution and to serve as a basis for selecting sites for more detailed scientific study by subsequent orbital and landing missions [e.g., Boeing Company, 1968a, b; Hansen, 1970; Kosofsky and El-Baz, 1970; Bowker and Hughes, 1971; Byers, 1977]. The coverage pattern included both the near and far sides of the Moon. Mission IV had significant differences in orbit parameters from the previous three missions as the craft was placed in a high altitude polar orbit. The mission had continuous solar illumination, which, with the different mission photo requirements, resulted in major changes in spacecraft operational employment, maneuver requirements and environmental control from the previous missions. Also collected on this mission were selenodetic, radiation intensity, and micrometeoroid impact data. The Lunar Orbiter IV spacecraft was launched from Cape Kennedy on 1967-05-04 at 22:25:00 UTC by an Atlas-Agena launch vehicle. Approximately 30 minutes after liftoff, the spacecraft was placed in a cislunar trajectory. On 1967-05-08 at 15:17 GMT the Lunar Orbiter was injected into a high altitude polar orbit of 2706 km x 6111 km with an inclination of 85.5 degrees and a period of 12 hours. The craft experienced Earth occultation periods. The spacecraft acquired photographs between 1967-05-11 and 1967-05-26 and readout occurred through 1967-06-01. Beginning on 1967-05-11 the camera's thermal door did not respond well to open and close commands. So that the thermal door would not be stuck in a closed position, making photography impossible, the door was kept open. Spacecraft maneuvers avoided condensation and light exposure and shots that were overexposed during apolune were later re-photographed at perilune. Later in the flight, readout advance irregularities began. Photography was terminated on 1967-05-26. Despite the problems, the entire film was read and transmitted and all but the last seven exposures were processed before the 'Bimat cut' on 1967-06-01. A total of 125 medium resolution (MR) and 141 high resolution (HR) frames (or ~420 HR subframes) were returned by Lunar Orbiter IV, and these images covered 99% of the Moon's near side [e.g., Hansen, 1970]. Accurate data were acquired from all other experiments throughout the mission. After Bimat cut, the orbit was lowered to gather orbital data for the later Lunar Orbiter V. Communication with Lunar Orbiter IV was lost after 70 days in orbit, on 1967-07-17. The spacecraft was used for tracking purposes until it impacted the lunar surface between ~26 degrees W longitude no later than 1967-10-31 due to the natural decay of the orbit. Mission IV was noted for the near-vertical photography of virtually all of the nearside, most at a ground resolution of 60 to 80 meters. Objectives ---------- Since Lunar Orbiters I, II and III had completed the requirements for Apollo mapping and site selection, the primary objective of Lunar Orbiter IV was a systematic photographic survey of lunar surface features for scientific knowledge and for added detail in site selection for subsequent missions [e.g., Boeing Company, 1968a, b; Hansen, 1970; Kosofsky and El-Baz, 1970; Bowker and Hughes, 1971; Byers, 1977]. The spacecraft acquired photographic data from 1967-05-11 to 1967-05-26, with readout continuing through 1967-06-01. Some of the early photos were degraded by light fogging of the film due to problems with the thermal door. The apolune photography sequence was modified to rephotograph these areas later in the flight. Although there were readout advance irregularities due to intermittent signals from the photo subsystem logic control circuitry, the implementation of slight changes in operating procedures allowed all but the last seven exposures to be processed before 'Bimat cut' was executed on 1967-05-26 during Orbit 36. The secondary objectives of Lunar Orbiter IV were to collect selenodetic, radiation intensity, and micrometeoroid impact data. Trajectory information improved the definition of the lunar gravitational field. Accurate data were acquired from these experiments throughout the mission. The radiation dosimetry measurement system functioned normally and provided data on the Earth's trapped radiation belts and on the radiation environment encountered by the spacecraft in transit to and near the Moon. One micrometeoroid hit was recorded during the photographic mission and four hits were recorded during the extended mission. The spacecraft was used for tracking purposes until it impacted the lunar surface. MISSION OPERATIONAL PHASES ========================== Mission phases were defined for significant spacecraft activity periods. For all five Lunar Orbiter missions, phases included at least the launch, trajectory, orbit insertion, orbital operations (primarily photographic imaging), and surface impact phases. The Lunar Orbiter IV spacecraft had three-axis stabilization and attitude control provided by four one-lb nitrogen gas jets [e.g., Boeing Company, 1968a, b]. The attitude reference for yaw and pitch was provided by five sun sensors about the spacecraft to provide spherical coverage and ensure Sun acquisition and lock-on to assist with realignment of solar panels. The roll axis reference was provided by an electro-optical sensor that tracked the star Canopus. This attitude resulted in the high-gain antenna being pointed toward Earth, with an assist from a rotatable boom on the unit. Signals from these sensing devices controlled N2 gas ejection from attitude control jets to acquire and maintain the necessary spacecraft orientation. Continuous solar illumination reduced the use of the Canopus tracker significantly. There was no difficulty in commanding accurate orientation of the spacecraft to support photography. Launch ------ The Lunar Orbiter IV spacecraft was launched from Cape Canaveral, Florida on 1967- 05-04 22:25:00 GMT on an azimuth of 100.8 degrees [e.g., Boeing, 1968a, b]. Launch was achieved using an Atlas-Agena D vehicle. Following separation from the Atlas, the Agena engine put the spacecraft into Earth orbit. The first- and second-stage boosters performed as programmed. Tracking and telemetry for the launch were provided by the Air Force Eastern Test Range (AFETR) Deep Space Network (DSN) and Manned Space Flight Network (MSFN) as elements of the Tracking and Data System (TDS). Spacecraft Id : 67-041A Target Name : MOON Mission Phase Start Time : 1967-05-04 Mission Phase Stop Time : 1967-05-04 Spacecraft Operations Type : ORBITER Cislunar Trajectory ------------------- Lunar Orbiter IV was injected into the cislunar trajectory at the end of the Agena second burn, approximately 30 minutes after liftoff. Separation of the Agena followed approximately 4 minutes later. The Canopus star tracker had difficulty acquiring Canopus at the first attempt, 6 hours, 50 minutes after launch, probably due to light reflections. A roll reference maneuver was staged during the first midcourse correction to correct this situation and approximately 2 hours later a successful star map was produced and Canopus as acquired at 08:25 GMT on 1967-05- 05. Spacecraft Id : 67-041A Target Name : MOON Mission Phase Start Time : 1967-05-04 Mission Phase Stop Time : 1967-05-08 Spacecraft Operations Type : ORBITER Lunar Orbit Insertion --------------------- A relatively large midcourse maneuver (a 78.34-degree roll, a 67.26 degree pitch and a velocity change of 60.86 m/s) was required to rotate the injection point from a 21o descending node orbit to an 85o ascending node orbit due to a change in the mission's objectives after initial programming. The velocity control rocket engine operated for 501.9 seconds, with a velocity reduction of 659.6 meters per second. The spacecraft was injected into a near-polar orbit around the Moon at 1967-05-08 at 15:17 GMT, 88 hours, 44 minutes hours after liftoff. The spacecraft achieved an initial orbit with an apolune of 6,114 km, a perilune of 2,706 km, and an orbital inclination of 85.48 degrees to the lunar equator and an orbital period of 12.01 hours. Initial orbit parameters were: apolune, 6,114 km; perilune 2,706 km; period, 721 minutes, and orbit inclination, 85.48 degrees. This orbit was used to conduct the photographic mapping mission. Spacecraft Id : 67-041A Target Name : MOON Mission Phase Start Time : 1967-05-08 Mission Phase Stop Time : 1967-05-11 Spacecraft Operations Type : ORBITER Lunar Imaging ------------- Active photography was initiated on Orbit 6 on 1967-05-11 at 15:46 GMT [e.g., Boeing Company, 1968a, b; Beeler and Michlovitz, 1969; Anderson and Miller, 1971]. During 30 successive photo orbits over 15 days, 199 dual-frame exposures were taken. With minor exceptions, two or three axis maneuvers were made for each photograph. The spacecraft made a total of 225 orbits over 70 days. The spacecraft acquired photographic data from 1967-05-11, during Orbit 6, to 1967-05-26, during Orbit 34. A total of 125 medium resolution (MR) and 141 high resolution (HR) frames (or ~420 HR subframes) were returned by Lunar Orbiter IV, and these images covered 99% of the Moon's near side [e.g., Hansen, 1970]. Final readout of data was completed during Orbit 48 on 1967-06-01. Spacecraft Id : 67-041A Target Name : MOON Mission Phase Start Time : 1967-05-11 Mission Phase Stop Time : 1967-06-01 Spacecraft Operations Type : ORBITER Surface Impact -------------- Communication with Lunar Orbiter IV was lost after 70 days in orbit, on 1967-07-17. The craft impacted the lunar surface due to the natural decay of the orbit no later than 1967-10-31 at ~26 degrees W longitude. Spacecraft Id : 67-041A Target Name : MOON Mission Phase Start Time : 1967-05-08 Mission Phase Stop Time : 1967-10-31 Spacecraft Operations Type : ORBITER LUNAR ORBIT SUMMARY =================== The success of the previous three Lunar Orbiter missions in achieving program objectives allowed Mission 4 to achieve more general scientific objectives [e.g., Boeing Company, 1968a, b]. The large change in the type of mission to be flown came after the launch vehicle boost trajectory had been programmed into the computer. Rather than delay the launch date, a midcourse maneuver that could produce the required change with no degradation of the overall velocity changes required for the rest of the mission was decided on. The orbit determination program (ODPL) for Mission 4 was performed without difficulty and maintained a high degree of accuracy. The midcourse guidance maneuver required to rotate the injection point in lunar plane from a 21o descending-node orbit to an 85o ascending-node orbit consisted of a 78.34o roll, a 67.26 degree pitch, and a velocity change of 60.85 meters per second (engine burn time 53.8 seconds). Although an orbital evaluation approximately five hours after the midcourse maneuver determined that a second maneuver of a 1.2 meter per second velocity change would be needed, instead the change was compensated for during the injection maneuver. The deboost maneuver on 1967-05-08 at 15:08:46 GMT injected the spacecraft into the initial lunar orbit. Final design of the deboost maneuver was based on 57 hours of ranging and two-way Doppler data. The 85-degree orbit inclination eliminated the Earth occultation period immediately after the deboost maneuver that had occurred in the previous three missions. The first orbit determination calculation was based on nearly two hours of tracking data from the first orbit. For the remainder of the mission, a data arc of one orbit (12 hours) provided near-optimum results. To avoid apolune and perilune and to provide complete coverage of all photo sites for subsequent analysis, the data arc epochs were placed at a true anomaly of about 245 degrees. The high apolune and perilune altitudes caused all orbit determinations to converge rapidly, making the effects of the lunar gravitational field very small. The purpose of tracking was to exercise and evaluate the tracking network and Apollo Orbit Determination Program. Celestial orientation was required for the first exposure in an orbit, and subsequent spacecraft maneuvers were computed as an additional maneuver increment from the previous orientation. Apolune photography maneuvers were based on a celestial reference orientation. During the photographic mission, 161 different photo maneuvers requiring 383 single-axis spacecraft maneuvers were determined and executed. Photo maneuvers were designed on the concept that perilune photos for successive orbits were taken at specific latitudes. The longitude coordinate was specified as a differential from the orbit trace for the specified latitudes. The differential longitudes were updated periodically to maintain the most favorable illumination. During the mission, an operational decision was made to rephotograph areas between 50 and 90 degrees E longitude because the perilune photos of this area were degraded by window fogging and light streaking. As the mission progressed, this area rotated into view for apolune photography and was properly illuminated. Photos were taken at +34 degrees latitude on five successive orbits, beginning on Orbit 29 to recover the desired photo data, but with a decrease in static resolution. The altitude range for photographs was 2670 to 6150 km. Lunar Orbiter IV was one of three spacecraft orbiting the Moon and operating on the same frequency so an offset track synchronization frequency was employed based on the best lock frequency of the transponder, ordinarily 330 Hz. OBSERVATIONAL STRATEGY AND RESULTS ================================== Lunar Orbiter IV performed a broad systematic survey of lunar surface features to increase the scientific knowledge of their nature origin and processes and to be a basis for selecting sites for more detailed scientific study by subsequent orbital and landing missions [e.g., Beeler and Michlovitz, 1969; Boeing Company, 1968a, b; Hansen, 1970; Anderson and Miller, 1971]. Photography was planned on the basis of the coverage to be obtained by the 610-mm camera to obtain vertical high-resolution photographs that would provide monoscopic coverage of the entire near side with a minimum of overlap. To achieve this, five single-frame sequences were taken on each of 29 consecutive passes. The 85o orbit had a perilune altitude at the equator of approximately 2700 km and the spacecraft was oriented with the long dimension of the frames in a north-south direction. Pole-to-pole coverage was obtained by taking, on each pass, four vertical photographs symmetrically spaced about the equator for coverage of the equatorial and temperate regions, and a fifth photograph for coverage of the polar regions and was taken slightly off vertical for lighting considerations. The nearside photography covered the equatorial regions with ground resolution of approximately 60 meters and the polar regions with ground resolutions of approximately 100 meters. The field of the 80-mm camera encompassed nearly the entire lunar disk. The 125 medium resolution and ~420 high resolution frames that were returned covered 99% of the Moon's near side with resolution between 58 meters and 134 meters. Mission IV coverage of the far side was obtained by five sequences taken near the apolune and by a number of near perilune sequences. The photographs taken near apolune consisted of seven medium resolution frames (two severely degraded); the high resolution frames covered essentially unilluminated areas. The most significant farside coverage was provided by medium resolution frames taken near perilune, with morning illumination. The photographs taken on the first pass covered extensive areas beyond the +90o longitude and each medium resolution frame taken on the polar sequences although centered on the nearside provided coverage that extended beyond the polar caps on the far side." END_OBJECT = MISSION_DESC OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "ANDERSON&MILLER1971" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BEELER&MICHLOVITZ1969" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BOEINGCO1968A" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BOEINGCO1968B" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BOWKER&HUGHES1971" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BYERS1977" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HANSEN1970" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KOSOFSKY&ELBAZ1970" END_OBJECT = MISSION_REFERENCE_INFORMATION END_OBJECT = MISSION_INFORMATION END_OBJECT = MISSION END