Description

Ranger 7 was designed to achieve a lunar impact trajectory and to transmit high-resolution photographs of the lunar surface during the final minutes of flight up to impact. The spacecraft carried six television vidicon cameras, 2 full-scan cameras (channel F, one wide-angle, one narrow-angle) and 4 partial scan cameras (channel P, two wide-angle, two narrow-angle) to accomplish these objectives. The cameras were arranged in two separate chains, or channels, each self-contained with separate power supplies, timers, and transmitters so as to afford the greatest reliability and probability of obtaining high-quality video pictures. No other experiments were carried on the spacecraft.

Spacecraft and Subsytems
Spacecraft and Subsystems

Rangers 6, 7, 8, and 9 were the so-called Block 3 versions of the Ranger spacecraft. The spacecraft consisted of a hexagonal aluminum frame base 1.5 m across on which was mounted the propulsion and power units, topped by a truncated conical tower which held the TV cameras. Two solar panel wings, each 73.9 cm wide by 153.7 cm long, extended from opposite edges of the base with a full span of 4.6 m, and a pointable high gain dish antenna was hinge mounted at one of the corners of the base away from the solar panels. A cylindrical quasiomnidirectional antenna was seated on top of the conical tower. The overall height of the spacecraft was 3.6 m.

Propulsion for the mid-course trajectory correction was provided by a 224-N thrust monopropellant hydrazine engine with 4 jet-vane vector control. Orientation and attitude control about 3 axes was enabled by 12 nitrogen gas jets coupled to a system of 3 gyros, 4 primary Sun sensors, 2 secondary Sun sensors, and an Earth sensor. Power was supplied by 9792 Si solar cells contained in the two solar panels, giving a total array area of 2.3 square meters and producing 200 W. Two 1200 Watt-hr AgZnO batteries rated at 26.5 V with a capacity for 9 hours of operation provided power to each of the separate communication/TV camera chains. Two 1000 Watt-hr AgZnO batteries stored power for spacecraft operations.

Communications were through the quasiomnidirectional low-gain antenna and the parabolic high-gain antenna. Transmitters aboard the spacecraft included a 60 W TV channel F at 959.52 MHz, a 60 W TV channel P at 960.05 MHz, and a 3 W transponder channel 8 at 960.58 MHz. The telecommunications equipment converted the composite video signal from the camera transmitters into an RF signal for subsequent transmission through the spacecraft high-gain antenna. Sufficient video bandwidth was provided to allow for rapid framing sequences of both narrow- and wide-angle television pictures.

Instruments

Television

The television system consisted of a six slow-scan vidicon TV cameras capable of transmitting high-resolution, close-up television pictures of the lunar surface during the final minutes of flight before the spacecraft impacted the lunar surface. These photographs provided large-scale topographic information needed for the Surveyor and Apollo projects. Vidicons 2.54 cm in diameter with an antimony-sulfide oxy-sulfide (ASOS) photoconductor target were used for image sensing in all six cameras. There were two camera channels which had independent power distribution networks so that the greatest reliability and probability of obtaining highest quality video pictures would be afforded. The first channel had two full-scan cameras, one wide angle (25 degree field of view and 25-mm focal length) designated the A-camera and one narrow angle (8.4 degree field of view and 76-mm focal length) B-camera. These cameras utilized an active image area of 11 sq mm that contained 1150 lines and was scanned in 2.5 sec. Scan and erase cycles were designed to act alternately resulting in intervals of 5 sec between consecutive pictures on a particular camera. The other channel had four partial-scan p-cameras, two narrow angle and two wide angle. The image area of these four cameras was 2.8 sq mm which contained 300 lines and was scanned in 0.2 sec. The instrument allowed for camera fields of view, ranging from 25 deg to 2.1 deg, to overlap and produce a 'nesting' sequence of pictures.

Electromagnetically driven slit-type shutters exposed the vidicons. Images were focused on the vidicon target, which was made up of a layer of photoconductive material initially charged by scanning with an electron beam. An electron beam then scanned the surface and recharged the photoconductor. The video signal was amplified several thousand times, sent to the transmitter where amplitude variations were converted to frquency variations, and were then transmitted directly to Earth. At the end of the active scan, the camera entered an erase cycle to prepare it for the next exposure. Twelve P-channel pictures were exposed between each F-channel picture.

The video transmissions were sent to a television receiver and recorded on both kinoscope film recorders and magnetic tape recorders. A cathode-ray tube reconstructed the original image, which was then photographed on 35-mm film. The full-scan camera system began transmitting pictures at 1308 UT on July 31, 1964, 17 min 13 sec prior to impact. The partial-scan system initiated transmission of pictures at 1312 UT, 13 min 40 sec prior to impact. The last full-scan transmission occured between 2.5 and 5 sec before impact, while the last partial-scan picture was taken between 0.2 and 0.4 sec before impact and achieved resolution to 0.5 m. Image motion is more severe in the last pictures. The experiment returned 4308 photographs of excellent quality. Selected photographs and a more complete description of the TV experiment are included in data set 64-041A-01B.

Launch-Orbit Information

Launch Information

Launch Date: 1964-07-28 at 16:50:00 UTC
Launch Vehicle: Atlas-Agena B
Launch Site: Cape Canaveral, United States
Decay Date: 1964-07-31
Mass: 365.7 kg kg Nominal Power: 200.0 W

Type: Lander

Central Body: Moon

Epoch start: 1964-02-02 09:24:33 UTC
Lander Coordinates
Latitude: -10.35°
Longitude: 339.4°
Regions Traversed
Lithosphere
Planet
The Moon

Mission Profile

The Atlas 250D and Agena B 6009 boosters performed nominally at launch inserting the Agena and Ranger into a 192 km altitude Earth parking orbit. Half an hour after launch the second burn of the Agena engine injected the spacecraft into a lunar intercept trajectory. After separation from the Agena, the solar panels were deployed, attitude control activated, and spacecraft transmissions switched from the omniantenna to the high-gain antenna. The next day, 29 July, the planned mid-course maneuver was initiated at 10:27 UT, involving a short rocket burn. The only anomaly during flight was a brief loss of two-way lock on the spacecraft by the DSIF tracking station at Cape Kennedy following launch.

Ranger 7 reached the Moon on 31 July. The F-channel began its one minute warm up 18 minutes before impact. The first image was taken at 13:08:45 UT at an altitude of 2110 km. Transmission of 4,308 photographs of excellent quality occurred over the final 17 minutes of flight. The final image taken before impact has a resolution of 0.5 meters. The spacecraft encountered the lunar surface in direct motion along a hyperbolic trajectory, with an incoming asymptotic direction at an angle of -5.57 degrees from the lunar equator. The orbit plane was inclined 26.84 degrees to the lunar equator. After 68.6 hours of flight, Ranger 7 impacted in an area between Mare Nubium and Oceanus Procellarum (subsequently named Mare Cognitum) at 10.63 S latitude, 20.60 W longitude. (Listed as 10.70 S, 339.33 E in the Apollo 16 Preliminary Science Report, 29-40, 1972.) Impact occurred at 13:25:48.82 UT at a velocity of 2.62 km/s. The spacecraft performance was excellent.

Total research, development, launch, and support costs for the Ranger series of spacecraft (Rangers 1 through 9) was approximately $170 million.

Summary