[meteorite-list] Mars Orbiter Mission Prepares for Mars Arrival

[Ron Baalke]

http://www.planetary.org/blogs/guest-blogs/2014/0916-laxman-mars-orbiter-mission-prepares.html

Mars Orbiter Mission prepares for Mars arrival
By Srinivas Laxman
September 16, 2014

The countdown for the crucial and nerve-wracking Mars orbit insertion 
of India's Mars Orbiter Mission (MOM) on September 24 has kicked off. 
At ISRO's telemetry, tracking and command network (ISTRAC) in Bangalore, 
the mood among  the scientists is right now a mixture of optimism, excitement, 
and nervous apprehension.

On September 15 at the auditorium of the Mars mission command and control 
centre at ISTRAC, some of the key players of this mission addressed the 
media about the sequence of events leading to the orbit insertion. Orbit 
insertion will take place 48 hours after NASA's Mars Atmosphere And Volatile 
Evolution Mission (MAVEN) enters the orbit of the Red Planet on September 
22.

ISRO's scientific secretary, V. Koteswara Rao, explained with a detailed 
power point presentation that on September 24, the insertion exercise 
will begin at T-3 hours at 4:17 a.m. when MOM will switch over to the 
medium gain antenna. At 6:56 a.m., 21 minutes prior to the start of the 
maneuver there spacecraft will rotate forward to point its engine.

Editor's note: all these times are India Standard Time, which is 5.5 hours 
ahead of UTC and 12.5 hours ahead of California. They are also Spacecraft 
Event Time, which does not account for the 12.5 minutes it will take for 
signals to reach Earth. Read this blog entry for a timeline in Earth Received 
Time for some common time zones. --ESL

The nail-biting moment will be at 7:17 a.m. The burn of the liquid apogee 
motor has to start and reduce the spacecraft's speed relative to Mars 
from 22.3 to 4.2 kilometers per second. It has to awaken after "sleeping" 
for 300 days. The scientists are hoping that it will revive autonomously 
responding to the commands which were uploaded on September 14 and 15. 
What is making the scientists nervous is that the burn will begin on the 
other side of the Red Planet and telemetry will stop at 7:22 a.m. They 
will receive confirmation that it has "woken up" only at 7:30 a.m. If 
the signal is positive it will be a moment for celebration. The engine 
will stop burning at 7:41 a.m. and communication with the spacecraft will 
be re-established at 7:47 a.m. This is called Plan A and if it is successful, 
it will be declared at about 8:15 a.m.

The liquid apogee motor will burn for 24 minutes and 14 seconds, consuming 
249.5 kilograms of propellant. If everything goes off without a hitch, 
MOM's orbit around Mars will be an ellipse ranging between 423 and 80,000 
kilometers from the surface.

 
[Image]
Mars Orbiter Mission's initial orbit

The initial, equatorial orbit of Mars orbiter mission will approach to 
within 423 kilometers of the surface at periapsis and stretch to 80,000 
kilometers away at apoapsis. Even at periapsis, it will orbit above Mars 
Odyssey and Mars Reconnaissance Orbiter. Mars Express does have an elliptical 
orbit, but it is near-polar and from 300 to 10,000 kilometers. Since its 
periapsis is not at the equator, Mars Express and Mars Orbiter Mission 
will not approach each other in the sky.

As with most global missions to the Red Planet there is a degree of uncertainty. 
What if Plan A does not work and the liquid apogee motor fails to "wake 
up?" To assess the state of the liquid apogee motor, it will be test fired 
for four seconds on September 22. This will be done along with a trajectory 
correction maneuver already planned for that day. On the same day MOM 
will enter the Mars sphere of influence too.

Koteswara Rao said that if the liquid apogee motor fails, Plan B will 
be implemented: using only the spacecraft's eight 22-Newton thrusters. 
He acknowledged that this will definitely not be a satisfactory scenario 
because it will result in the consumption of all the spacecraft's fuel. 
What is worse, the orbit will not be a good one for science. Asked if 
the implementation of Plan B will mean compromising on the science profile 
of the mission, he diplomatically responded that "some science you may 
lose, some science you may gain."

But MOM project director Subbiah Arunan expressed confidence that the 
motor will not play spoilsport, because during the rigorous tests and 
simulations it underwent for prolonged periods it operated without a hitch.

This is a rare case when two Mars spacecraft will be arriving almost simultaneously 
- MOM and MAVEN. To ensure complete co-ordination NASA and ISRO scientists 
have been constantly in touch through teleconferencing. Arunan said that 
about 250 NASA workers will be at their stations at the Goldstone and 
Canberra Deep Space Network stations to monitor MOM’s Mars orbit insertion 
on September 24.

In addition, Arunan said that four 70-meter dish antennas - two each at 
Goldstone and Canberra - have been dedicated to MOM's orbit insertion 
on September 24. He said that the first signal of the status of the orbit 
insertion will be acquired by the Canberra Deep Space Network, which will 
be flashed to the Mars mission command and control centre at Bangalore.

While scientists at the Mars mission command and control centre are gearing 
up for MOM's entry to the Red Planet, the Indian Space Science Data Centre 
is also preparing for the historic occasion. The Centre is a part of ISTRAC 
located in the campus of the Indian Deep Space Network at Byalalu off 
the Bangalore-Mysore highway.

J. D. Rao, general manager of the Indian Space Science Data Centre, said 
that data from the five payloads from MOM will be acquired and then processed, 
stored, archived and disseminated by this unit. He said that data from 
the payloads will arrive simultaneously at a rate of four kilobits per 
second. "For further processing and analysis it will be sent to the principal 
investigators," he said, while pointing out that it was his responsibility 
to archive the data for a long period, which he described as quite a challenge.

The scientists at the centre are looking forward to receiving the first 
picture from MOM's colour camera----this will be an emotional moment!