The innovative use of Pressurant Extends Messenger's mission has enabled the Messenger spacecraft to collect more data before the spacecraft finish using most of its propellant.
Engineers on the team have come up with a way to use the pressurization gas in the spacecraft's propulsion system to propel Messenger spacecraft for as long as another month, that will allow scientists to collect even more data about the planet closest to the Sun.
Messenger Mission Systems Engineer Dan O'Shaughnessy, of the Johns Hopkins University Applied Physics Laboratory, in Laurel, Md, said that Messenger has used nearly all of the onboard liquid propellant. Typically, when this liquid propellant is completely exhausted, a spacecraft can no longer make adjustments to its trajectory and for Messenger, this would have meant that they would no longer have been able to delay the inevitable impact with Mercury's surface.
Stewart Bushman, lead propulsion engineer for the mission to his knowledge this is the first time that helium Pressurant has been intentionally used as a cold-gas propellant through hydrazine thrusters. These engines are not optimized to use pressurized gas as a propellant source. They have flow restrictors and orifices for hydrazine that reduce the feed pressure, hampering performance compared with actual cold-gas engines, which are little more than valves with a nozzle.
APL's Haje Korth, the instrument scientist for the Magnetometer, said that during the additional period of operations, up to four weeks, Messenger will measure variations in Mercury's internal magnetic field at shorter horizontal scales than ever before, scales comparable to the anticipated periapsis altitude between 7 km and 15 km above the planetary surface.
Messenger periapsis altitude is now approximately 101 kilometers and decreasing. The next orbit-correction maneuver on January 21, 2015, will raise the altitude at closest approach from approximately 25 kilometers to just over 80 kilometers.