NASA Spacecraft Has Entered Orbit Around Mercury
WASHINGTON, D.C. — [UPDATE 10:05 PM EDT, Thursday Mar. 17] A NASA spacecraft began orbiting Mercury Thursday, becoming the first to fly around the solar system’s innermost planet, the space agency said.
NASA’s MESSENGER spacecraft successfully entered orbit around Mercury around 9:00 pm (0200 GMT) and will circle the planet for one Earth year in an unprecedented study of the tiny, hot planet that is closest to the Sun.
The craft began its journey more than six years ago, traveling though the inner solar system and embarking on flybys of Earth, Venus and Mercury.
“MESSENGER is orbiting Mercury!” said Bill Nye, Executive Director of the Planetary Society. “It’s rocket science at its best. Before this success, Mercury was the only inner planet that had never been orbited by a spacecraft.”
“MESSENGER’s going into orbit is a momentous accomplishment in humanity’s quest to explore the solar system,” said Bruce Betts, the Planetary Society’s Director of Projects. “The mission has already helped us complete humanity’s initial reconnaissance of the inner solar system, and provided ground breaking science to help us understand fascinating and exotic Mercury.”
It will be the first ever spacecraft to orbit Mercury when it fires its largest thruster at 8:45 pm (0045 GMT Friday) in a 14-minute maneuver to slow down so it can enter its trajectory around Mercury, NASA said.
“The orbit insertion will place the spacecraft into a 12-hour orbit about Mercury with a 200-kilometer (124-mile) minimum altitude,” the US space agency said.
NASA’s MErcury Surface, Space ENvironment, GEochemistry and Ranging, or MESSENGER, is scheduled to enter the planet’s orbit at approximately 9 p.m. after conducting more than a dozen laps through the inner solar system for the past 6.6 years.
MESSENGER will be 46.14 million kilometers (28.67 million miles) from the Sun and 155.06 million kilometers (96.35 million miles) from Earth when it heads into Mercury’s orbit, NASA said.
MESSENGER has been on a six-year mission to become the first spacecraft to orbit Mercury. The spacecraft followed a path through the inner solar system, including one flyby of Earth, two flybys of Venus, and three flybys of Mercury.
The first NASA craft to study Mercury since the Mariner mission more than three decades ago, MESSENGER has already been able to return a partial map of the planet’s crater-filled surface after a handful of flybys.
“Orbit insertion is the last hurdle to a new game level, operation of the first spacecraft in orbit about the solar system’s innermost planet,” said principal investigator Sean Solomon of the Carnegie Institution of Washington.
“The MESSENGER team is ready and eager for orbital operations to begin.”
The craft is carrying seven science instruments, including a Mercury Dual Imaging System (MDIS), the Mercury Atmospheric and Surface Composition Spectrometer (MASCS), and the Energetic Particle and Plasma Spectrometer (EPPS).
It was first launched in August 2004 and has since traveled 4.9 billion miles (about 7.9 billion kilometers) through “a range of extreme conditions,” NASA said.
On March 7, antennas from each of the three Deep Space Network (DSN) ground stations began continuous monitoring, allowing flight control engineers at the Johns Hopkins University Applied Physics Laboratory to observe MESSENGER on its final approach to Mercury. The spacecraft also began executing the last cruise command sequence of the mission, when the command sequence containing the orbit-insertion burn will start.
“This is a milestone event for our small, but highly experienced, operations team, marking the end of six and one half years of successfully shepherding the spacecraft through six planetary flybys, five major propulsive maneuvers, and sixteen trajectory-correction maneuvers, all while simultaneously preparing for orbit injection and primary mission operations,” said MESSENGER Systems Engineer Eric Finnegan.
“Whatever the future holds, this team of highly dedicated engineers (http://messenger.jhuapl.edu/moc/index.html) has done a phenomenal job methodically generating, testing, and verifying commands to the spacecraft, getting MESSENGER where it is today.”
— portions of this story are ©AFP