Mariner 6 and 7
Mission type | Flyby Mars |
---|---|
Operator | NASA / JPL |
COSPAR ID | 1969-014A |
SATCAT no. | 3759 |
Mission duration | 1 year, 9 months and 27 days |
Spacecraft properties | |
Manufacturer | Jet Propulsion Laboratory |
Launch mass | 381 kg[1] |
Power | 449 W |
Start of mission | |
Launch date | February 25, 1969, 01:29:02 LC-36B | UTC
End of mission | |
Disposal | Decommissioned |
Deactivated | December 23, 1970 |
Flyby of Mars | |
Closest approach | July 31, 1969 |
Distance | 3,431 kilometers (2,132 mi) |
Mission type | Flyby Mars |
---|---|
Operator | NASA / JPL |
COSPAR ID | 1969-030A |
SATCAT no. | 3837 |
Mission duration | 1 year and 9 months |
Spacecraft properties | |
Manufacturer | Jet Propulsion Laboratory |
Launch mass | 381 kg[3] |
Power | 449 W |
Start of mission | |
Launch date | March 27, 1969, 22:22:00 LC-36A | UTC
End of mission | |
Disposal | Decommissioned |
Deactivated | December 28, 1970 |
Flyby of Mars | |
Closest approach | August 5, 1969 |
Distance | 3,430 kilometers (2,130 mi) |
Mariner 6 and Mariner 7 (Mariner Mars 69A and Mariner Mars 69B) were two uncrewed
Launch
Three Mariner probes were constructed for the mission, with two intended to fly and one as a spare in the event of a mission failure. The spacecraft were shipped to Cape Canaveral with their Atlas-Centaur boosters in December 1968 – January 1969 to begin pre-launch checkouts and testing. On February 14, Mariner 6 was undergoing a simulated countdown on LC-36A, electrical power running, but no propellant loaded in the booster. During the test run, an electrical relay in the Atlas malfunctioned and opened two valves in the pneumatic system which allowed helium pressure gas to escape from the booster's balloon skin. The Atlas began to crumple over, however two pad technicians quickly activated a manual override switch to close the valves and pump helium back in. Although Mariner 6 and its Centaur stage had been saved, the Atlas had sustained structural damage and could not be reused, so they were removed from the booster and placed atop Mariner 7's launch vehicle on the adjacent LC-36B, while a different Atlas was used for Mariner 7.
NASA awarded the quick-thinking technicians, Bill McClure and Charles (Jack) Beverlin, an Exceptional Medal of Bravery for their courage in risking being crushed underneath the 124-foot (38 m) rocket. In 2014, an escarpment on Mars which NASA'S Opportunity rover had recently visited was named the McClure-Beverlin Ridge in honor of the pair, who had since died.[6][7][8]
Mariner 6 lifted off from LC-36B at Cape Canaveral on February 25, 1969, using the Atlas-Centaur AC-20 rocket, while Mariner 7 lifted off from LC-36A on March 27, using the Atlas-Centaur AC-19 rocket. The boost phase for both spacecraft went according to plan and no serious anomalies occurred with either launch vehicle. A minor LOX leak froze some telemetry probes in AC-20 which registered as a drop in sustainer engine fuel pressure; however, the engine performed normally through powered flight. In addition, BECO occurred a few seconds early due to a faulty cutoff switch, resulting in longer than intended burn time of the sustainer engine, but this had no serious effect on vehicle performance or the flight path. AC-20 was launched at a 108-degree azimuth.[9]
The Centaur stage on both flights was set up to perform a retrorocket maneuver after capsule separation. This served two purposes, firstly to prevent venting propellant from the spent Centaur from contacting the probe, secondly to put the vehicle on a trajectory that would send it into solar orbit and not impact the Martian surface, potentially contaminating the planet with Earth microbes.
Spaceflight
On July 29, 1969, less than a week before closest approach, Jet Propulsion Laboratory (JPL) lost contact with Mariner 7. The center regained the signal via the backup low-gain antenna and regained use of the high gain antenna again shortly after Mariner 6's close encounter. Leaking gases from a battery (which later failed) were thought to have caused the anomaly.[4] Based on the observations that Mariner 6 made, Mariner 7 was reprogrammed in flight to take further observations of areas of interest and actually returned more pictures than Mariner 6, despite the battery's failure.[10]
Closest approach for Mariner 6 occurred July 31, 1969, at 05:19:07 UT[5] at a distance of 3,431 kilometers (2,132 mi)[5] above the martian surface. Closest approach for Mariner 7 occurred August 5, 1969 at 05:00:49 UT[4] at a distance of 3,430 kilometers (2,130 mi) above the Martian surface. This was less than half of the distance used by Mariner 4 on the previous US Mars flyby mission.[10]
Both spacecraft are now defunct and in heliocentric orbits.[10]
Science data and findings
By chance, both spacecraft flew over cratered regions and missed both the giant northern volcanoes and the equatorial grand canyon discovered later. Their approach pictures did, however, photograph about 20 percent of the planet's surface,[10] showing the dark features long seen from Earth – in the past, these features had been mistaken for canals by some ground-based astronomers. When Mariner 7 flew over the Martian south pole on August 4, 1969, it sent back pictures of ice-filled craters and outlines of the south polar cap.[11] Despite the communication defect suffered by Mariner 7 earlier, these pictures were of better quality than what had been sent by its twin, Mariner 6, a few days earlier when it flew past the Martian equator.[12] In total, 201 photos were taken and transmitted back to Earth, adding more detail than the earlier mission, Mariner 4.[10] Both crafts also studied the atmosphere of Mars.
Coming a week after Apollo 11, Mariner 6 and 7's flyby of Mars received less than the normal amount of media coverage for a mission of this significance.
The ultraviolet spectrometer onboard Mariners 6 and 7 was constructed by the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP).[13]
The engineering model of Mariners 6 and 7 still exists, and is owned by the Jet Propulsion Laboratory (JPL). It is on loan to LASP, and is on display in the lab's lobby.
Mariner 6 and 7 infrared radiometer observations helped to trigger a scientific revolution in Mars knowledge.[14][15] The Mariner 6 and 7 infrared radiometer results showed that the atmosphere of Mars is composed mostly of carbon dioxide (CO2), and they were also able to detect trace amounts of water on the surface of Mars.[14]
Spacecraft and subsystems
The Mariner 6 and 7 spacecraft were identical, consisting of an octagonal
The spacecraft was attitude stabilized in three axes, referenced to the Sun and the star
Three telemetry channels were available for telecommunications. Channel A carried engineering data at 8⅓ or 33⅓ bit/s, channel B carried scientific data at 66⅔ or 270 bit/s and channel C carried science data at 16,200 bit/s. Communications were accomplished through the high- and low-gain antennas, via dual S-band
Instrumentation:
- IR Spectrometer
- Two-Channel IR Radiometer Mars Surface Temperature
- UV Spectrometer
- S-Band Occultation
- Thermal Control Flux Monitor (Conical Radiometer)
- Mars TV Camera
- Celestial Mechanics
- General Relativity
See also
- List of missions to Mars
- Space exploration
- Uncrewed space missions
- Heat Flow and Physical Properties Package (included an infrared radiometer for the Martian surface)
References
- ^ "Mariner 6". NASA's Solar System Exploration website. Retrieved November 30, 2022.
- National Space Science Data Center. Retrieved December 28, 2011.
- ^ "Mariner 7". NASA's Solar System Exploration website. Retrieved November 30, 2022.
- ^ a b c d "Mariner 7: Details". National Space Science Data Center. Retrieved December 28, 2011.
- ^ a b c "Mariner 6: Details". National Space Science Data Center. Retrieved December 28, 2011.
- ^ Opportunity's Southward View of 'McClure-Beverlin Escarpment', NASA, 2014, archive
- ^ Billy McClure obituary, 508th Parachute Regiment (veterans's association), 2009; archive
- ^ Charles Beverlin obituary, Dignity Memorial (commercial web site), 2013
- ^ Mariner-Mars 1969: A Preliminary Report NASA SP-225, p21
- ^ a b c d e
Pyle, Rod (2012). Destination Mars. Amherst, N.Y: ISBN 978-1-61614-589-7.
- ISSN 0971-751X. Retrieved August 10, 2019.
- ISSN 0362-4331. Retrieved August 10, 2019.
- PMID 20094543.
- ^ a b "Infrared Spectrometer and the Exploration of Mars". American Chemical Society. Retrieved August 10, 2019.
- PMID 20072273.
External links
- Mariner Mars 1969 Launches - Press Kit
- Tracking and data system support for the Mariner Mars 1969 mission. Volume 1 - Planning phase through midcourse maneuver
- Tracking and data system support for the Mariner Mars 1969 mission. Volume 2: Midcourse maneuver through end of nominal mission
- Tracking and data system support for the Mariner Mars 1969 mission. Volume 3: Extended operations mission
- The Mariner 6 and 7 flight paths and their determination from tracking data
- Two over Mars - Mariner 6 and Mariner 7, February - August 1969
- Mariner 6 Mission Profile by NASA's Solar System Exploration
- Mariner 7 Mission Profile by NASA's Solar System Exploration
- Mariner 6 and 7 Data Set Information (highly technical)
- Mariner 6 and 7 Data Viewer Page (includes many images)
- Page with reprocessed Mariner 7 images
- Mariner 6 and 7 images