Mission Type: Lander, Orbiter
Launch Vehicle: Titan IIIE-Centaur (TC-4 / Titan no. E-4 / Centaur D-1T)
Launch Site: Cape Canaveral, Florida, USA
NASA Center: Jet Propulsion Laboratory, Langley Research Center
Spacecraft Mass: 3,527 kg
Spacecraft Instruments:
Orbiter:
1) imaging system
2) atmospheric water detector
3) infrared thermal mapper
Lander:
1) imaging system
2) gas chromatograph mass spectrometer
3) seismometer
4) x-ray fluorescence
5) biological laboratory
6) weather instrument package (temperature, pressure, wind velocity)
7) remote sampler arm
Aeroshell:
1) retarding potential analyzer
2) upper-atmosphere mass spectrometer
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24

NSSDC Master Catalog, http://nssdc.gsfc.nasa.gov/nmc/

Viking 1 was the first of a pair of complex deep space probes that were designed to reach Mars and collect evidence on the possibility (or lack thereof) for life on Mars.

Each spacecraft was composed of two primary elements, an orbiter (2,339 kilograms) and a lander (978 kilograms). The orbiter design heavily borrowed from the Mariner buses, while the lander looked superficially like a much larger version of the Surveyor lunar lander.

Prior to launch, the batteries of the first spacecraft were discharged, prompting NASA to replace the original first spacecraft with the second, which was launched as Viking 1.

After three midcourse corrections (on 27 August 1975 and 10 and 15 June 1976), the spacecraft entered orbit around Mars on 19 June 1976. Initial orbital parameters were 1,500 x 50,300 kilometers. The following day, when the orbiter began transmitting back photos of the primary landing site in the Chryse region, scientists discovered that the area was rougher than expected.

Using the new photos, scientists targeted the lander to a different site on the western slopes of Chryse Planitia. The lander separated from the orbiter, and after a complex atmospheric entry sequence, during which the probe took air samples, Viking 1 lander set down safely at 22.483° north latitude and 47.94° west longitude at 11:53:06 UT on 20 July 1976.

Once down, the spacecraft began taking high quality photographs (in three colors) of its surroundings. Instruments recorded temperatures ranging from -86°C (before dawn) to -33°C (in the afternoon). The seismometer on the lander was inoperable.

On 28 July, the lander's robot arm scooped up the first soil samples and deposited them into a special biological laboratory that included a gas chromatograph mass spectrometer. While some data could be construed as indicating the presence of life, a major test for organic compounds gave negative Results.

The lander continued to return daily (and then eventually weekly) weather reports until loss of contact on 1 February 1983. Further attempts to regain contact proved unsuccessful. The orbiter was shut down on 7 August 1980, after it ran out of attitude-control propellant.