Washington, Feb 20 - NASA's Mars Atmosphere and Volatile Evolution has completed the first of five deep-dip maneuvers designed to gather measurements closer to the lower end of the Martian upper atmosphere.

Bruce Jakosky of the University of Colorado said that during normal science mapping, they make measurements between an altitude of about 150 km and 6,200 km (93 miles and 3,853 miles) above the surface and during the deep-dip campaigns, they lower the lowest altitude in the orbit, known as periapsis, to about 125 km (78 miles) which allows them to take measurements throughout the entire upper atmosphere.

The 25 km (16 miles) altitude difference may not seem like much, but it allows scientists to make measurements down to the top of the lower atmosphere. At these lower altitudes, the atmospheric densities are more than ten times what they are at 150 km (93 miles).

Jakosky added that they are interested in the connections that run from the lower atmosphere to the upper atmosphere and then to escape to space and they are measuring all of the relevant regions and the connections between them.

The first deep dip campaign ran from Feb. 10 to 18. The first three days of this campaign were used to lower the periapsis. Each of the five campaigns lasts for five days allowing the spacecraft to observe for roughly 20 orbits. Since the planet rotates under the spacecraft, the 20 orbits allow sampling of different longitudes spaced around the planet, providing close to global coverage.

Feb month's deep dip maneuvers began when team engineers fired the rocket motors in three separate burns to lower the periapsis. The engineers did not want to do one big burn, to ensure that they didn't end up too deep in the atmosphere. So, they "walked" the spacecraft down gently in several smaller steps.

At the end of the campaign , two maneuvers were conducted to return MAVEN to normal science operation altitudes. Science data returned from the deep dip will be analyzed over the coming weeks. The science team will combine the results with what the spacecraft has seen during its regular mapping to get a better picture of the entire atmosphere and of the processes affecting it. (ANI)