Apollo 18 was originally planned in July 1969 to land in the moon's Schroter's Valley, a riverlike channel-way. The original February 1972 landing date was extended when NASA cancelled the Apollo 20 mission in January 1970. Later in the planning process the most likely landing site was the crater Gassendi. Finally NASA cancelled Apollo 18 and 19 on 2 September 1970 because of congressional cuts in FY 1971 NASA appropriations. There was also a feeling after the Apollo 13 emergency that NASA risked having its entire manned space program cancelled if a crew was lost on another Apollo mission. Total savings of cancelling the two missions (since the hardware was already built and the NASA staff had to stay in place for the Skylab program) was only $42.1 million. Before the cancellation, Schmitt was pressing for a more ambitious landing in Tycho or the lunar farside. Pressure from the scientific community resulted in geologist Schmitt flying on Apollo 17, the last lunar mission, bumping Joe Engle from the lunar module pilot slot. References: 16 , 366 .

Development took eight years, and cost 2 billion 1986 ECU's.

High resolution photo reconnaissance mission. References: 279 .

Continued operation of the long-range telephone and telegraph radio-communication system within the Soviet Union and transmission of USSR central television programmes to stations in the Orbita and participating international networks (international coope ration scheme). References: 1 , 2 , 5 , 6 .

KH-9 type satellite. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A). References: 1 , 2 , 5 , 6 .

Improved TIROS Operational System. References: 5 , 126 .

Failed; did not enter Martian orbit as planned; intended to be a Mars orbiter mission. Mars 4 reached Mars on 10 February 1974. Due to use of helium in preflight tests of the computer chips, which resulted in degradation of the chips during the voyage to Mars, the retro-rockets never fired to slow the craft into Mars orbit. Mars 4 flew by the planet at a range of 2,200 km. It returned one swath of pictures and some radio occultation data. Final heliocentric orbit 1.02 x 1.63 AU, 2.2 degree inclination, 556 day period. References: 1 , 2 , 5 , 6 , 67 , 118 , 274 , 296 .

High resolution photo reconnaissance satellite; returned film capsule; maneuverable. References: 1 , 2 , 6 .

Mars probe intended to enter Martian orbit and comprehensively photograph Mars. Parameters are for Mars orbit. Mars 5 reached Mars on 12 February 1974 and was inserted into a 1760 km x 32,586 km orbit. Due to computer chip failures the orbiter operated only a few days and returned atmospheric data and images of a small portion of the Martian southern hemisphere. References: 1 , 2 , 5 , 6 , 67 , 118 , 274 , 296 .

Continued maintenance of the Skylab space station and extensive scientific and medical experiments. Installed twinpole solar shield on EVA; performed major inflight maintenance; doubled record for length of time in space. Completed 858 Earth orbits and 1,081 hours of solar and Earth experiments; three EVAs totalled 13 hours, 43 minutes.

The space vehicle, consisting of a modified Apollo command and service module payload on a Saturn IB launch vehicle, was inserted into a 231.3 by 154.7 km orbit. Rendezvous maneuvers were performed during the first five orbits as planned. During the rendezvous, the CSM reaction control system forward firing engine oxidizer valve leaked. The quad was isolated. Station-keeping with the Saturn Workshop began approximately 8 hours after liftoff, with docking being performed about 30 minutes later. Additional Details: Skylab 3. References: 1 , 2 , 5 , 6 , 33 , 60 .

Area survey photo reconnaissance satellite; returned film capsule. References: 1 , 2 , 6 .

Planned date of third manned MOL mission at time of the program cancellation. References: 128 .

First glide flight. Maximum Speed - 740 kph. Maximum Altitude - 12190 m. Flight Time - 252 sec. References: 49 , 97 .

Mars probe intended to make a soft landing on Mars. Total fueled launch mass of the lander and orbital bus was 3260 kg. It reached Mars on 12 March 1974, separated from the bus, and entered the atmosphere, where a parachute opened, slowing the descent. As the probe descended through the atmosphere it transmitted data for 150 seconds, representing the first data returned from the atmosphere of Mars. Unfortunately, the data were largely unreadable due to a flaw in a computer chip which led to degradation of the system during its journey to Mars. When the retro-rockets fired for landing, contact was lost with the craft. Mars 6 landed at about 24 degrees south, 25 degrees west in the Margaritifer Sinus region of Mars. Bus ended up in a final heliocentric orbit 1.01 x 1.67 AU, 2.2 degree inclination, 567 day period. References: 1 , 2 , 5 , 6 , 67 , 118 , 274 , 296 .

Soft landed on Mars 3/12/74. References: 1 , 2 , 5 , 6 , 67 , 118 , 274 .

Installed second sunshade. Replaced solar camera film cartridges. During EVA by crew members of Skylab 3, a twin-boom sunshade, developed by MSFC, was deployed over the parasol of the OWS. A redesigned and refined thermal parasol had been launched with Skylab 3. However, its use would have required jettisoning the parasol deployed by crew members of Skylab 2, with the possibility of creating the same thermal problems that existed on the OWS prior to the parasol deployment. Following erection of the twin-pole sunshade, the cabin temperature stayed at a comfortable 293-297 K (67.7°F-74.9°F). References: 66 .

National Air and Space Museum Director Michael Collins advised JSC that NASM had established a center for research and study with responsibility for a complete library of lunar photos to document scientific results of the Apollo missions. The library would be used for original research and for planning and updating scientific parts of exhibits. References: 16 .

Mars probe intended to make a soft landing on Mars. Mars 7 reached Mars on 9 March 1974. Due to a problem in the operation of one of the onboard systems (attitude control or retro-rockets) the landing probe separated prematurely and missed the planet by 1,300 km. The early separation was probably due to a computer chip error which resulted in degradation of the systems during the trip to Mars. Ended up in a final heliocentric orbit 1.01 x 1.69 AU, 2.2 degree inclination, 574 day period. References: 1 , 2 , 5 , 6 , 67 , 118 , 274 , 296 .

Mars probe intended to make a soft landing on Mars. Solar Orbit (Heliocentric). References: 1 , 2 , 5 , 6 , 67 , 118 , 274 .

NASA decided to delete the Skylab backup Saturn V Orbital Workshop launch capability effective 15 August. All work associated with the completion, checkout, and support of Skylab backup hardware, experiments, software, facilities, and ground support equipment would be canceled immediately, except for the work that would directly support SL-3, SL-4, and rescue missions.

U.S. bombing of Cambodia ends, marking official halt to 12 years of combat activity in Southeast Asia

Defense Meteorological Satellite Program. References: 1 , 2 , 5 , 6 .

Maximum Speed - 722 kph. Maximum Altitude - 13720 m. Flight Time - 267 sec. References: 49 , 97 .

High resolution photo reconnaissance satellite; returned film capsule; maneuverable. References: 1 , 2 , 6 .

Investigation of the upper atmosphere and outer space. References: 1 , 2 , 5 , 6 , 99 .

Over Atlantic Ocean. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C). Launch vehicle put payload into geosynchronous transfer orbit References: 1 , 2 , 5 , 6 , 278 .

High resolution photo reconnaissance satellite; returned film capsule; maneuverable. References: 1 , 2 , 6 .

Replaced solar camera film cartridges; installed replacement gyroscopes. References: 66 .

Apollo Soyuz Test Project Program Director Chester M. Lee, Office of Manned Space Flight, NASA Hq., was assigned as the management official to take actions necessary for the final phaseout of the Apollo program. All Apollo program inquiries, activities, and actions not covered by specific delegations of authority would be referred to Lee for appropriate decision and disposition. References: 16 .

Possible ELINT satellite. References: 1 , 2 , 5 , 6 .

Area survey photo reconnaissance satellite; returned film capsule; separated capsule. References: 1 , 2 , 6 .

Uncertain if Molniya-1T model was Molniya-1 or Molniya-1T. Operation of a system of long range telephone-telegraph radiocommunication, and transmission of USSR Central Television programmes to the stations of the Orbita network. References: 1 , 2 , 5 , 6 .

Guidelines were issued by NASA Hq for release, disposition, and storage of all unneeded Skylab Program equipment. Two Saturn Vs, two Saturn IBs, three command and service modules, the backup Skylab cluster, and appropriate spares would be placed in minimum cost storage as soon as program requirements permitted.

Maximum Speed - 771 kph. Maximum Altitude - 13720 m. Flight Time - 277 sec. References: 49 , 97 .

Influenced by the stranded Skylab crew portrayed in the book and movie 'Marooned', NASA provided a crew rescue capability for the only time in its history. A kit was developed to fit out an Apollo command module with a total of five crew couches. In the event a Skylab crew developed trouble with its Apollo CSM return craft, a rescue CSM would be prepared and launched to rendezvous with the station. It would dock with the spare second side docking port of the Skylab docking module. During Skylab 3, one of the thruster quads of the Apollo service module developed leaks. When the same problem developed with a second quad, the possibility existed that the spacecraft would not be maneuverable. Preparation work began to fit out a rescue CSM, and astronauts Vance Brand and Don Lind began preparations to rescue astronauts Bean, Garriott, and Lousma aboard the station. However the problem was localized, work arounds were developed, and the first space rescue mission was not necessary. The Skylab 3 crew returned successfully in their own Apollo CSM at the end of their 59 day mission. References: 33 .

Planned second mission to the Salyut DOS 3 space station (Cosmos 557). Cancelled after it failed in orbit. References: 344 .

High resolution photo reconnaissance satellite; returned film capsule; maneuverable. References: 1 , 2 , 6 .

Investigation of the upper atmosphere and outer space. References: 1 , 2 , 5 , 6 .

Discussions confirmed that there was reasonable assurance that an Apollo-Soyuz Test Project (ASTP) revisit to Skylab in mid-1975 was feasible. However, such a dual mission would create a significant planning problem for the operations team and would introduce many new considerations to the inflight planning and execution because of uncertainties in the orbital mechanics.

Military navigation satellite. References: 1 , 2 , 5 , 6 .

Maximum Speed - 724 kph. Maximum Altitude - 13720 m. Flight Time - 271 sec. References: 49 , 97 .

Second flight of Soyuz U launch vehicle. High resolution photo reconnaissance satellite; returned film capsule; maneuverable. References: 1 , 2 , 6 .

Replaced film cartridges for solar camera. References: 66 .

KH-8 type satellite. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A). References: 1 , 2 , 5 , 6 .

Experimental flight for the purpose of further development of manned space craft Soyuz 7K-T modifications. After the Soyuz 11 disaster, the Soyuz underwent redesign for increased reliability. Two solo test flights of the new design were planned. Crews for the first flight were those already planned for the deferred follow-on missions to the failed DOS 2 and DOS 3 space stations. Recovered September 29, 1973 13:14 GMT. Landed 400 km SW Karaganda. References: 1 , 2 , 6 , 32 , 33 , 60 .