Solar Conjunction Ends: Nirgal Vallis
28 September 2004
For the past several weeks, Mars was on the other side of the Sun relative to Earth. During this period, known as solar conjunction, radio communication with spacecraft orbiting and roving on Mars was limited. As is always done during solar conjunction, on 7 September 2004, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) was turned off. On Saturday, 25 September 2004, the MOC team gathered at Malin Space Science Systems to command the instrument to turn back on again. After a successful turn-on, MOC acquired its first narrow angle camera image, shown here, on orbit 24808 (24,808th orbit since the start of the Mapping phase of the MGS mission in March 1999).
The 25 September image shows a portion of Nirgal Vallis, an ancient valley system in the Mare Erythraeum region of Mars. The valley floor is covered by large, ripple-like bedforms created by wind. This early southern winter image is located near 27.4°S, 42.9°W, and covers an area approximately 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left.
This was the 4th solar conjunction period that MGS and MOC have been through since the spacecraft reached the red planet in September 1997. The four solar conjunction periods, where MOC was turned off, were:
- First solar conjunction: 29 April - 1 June 1998
- Second solar conjunction: 22 June - 12 July 2000
- Third solar conjunction: 1 August - 18 August 2002
- Fourth solar conjunction: 7 September - 25 September 2004.
In late October, MGS MOC will mark the start of its fourth Mars year since the beginning of the Mapping Phase of the mission in March 1999. MGS and MOC have already been orbiting Mars for more than 4 Mars years, including the pre-Mapping aerobrake and science phasing orbit insertion periods.