Chandrayaan’s temperature rises, mission scientists not sweating yet

A significant rise in temperature inside Chandrayaan — as a result of the spacecraft getting nearer to the sun while going around the moon— is preventing India’s first lunar mission from entering into the operational phase.

The high temperatures are likely to continue at least till the middle of next month when the spacecraft will move sufficiently away from the sun for the heat to subside. Though this rise in temperature was entirely expected and not a cause for any concern, the scientists at the mission control in Bangalore are playing safe by not switching on all the instruments simultaneously so as to avoid further rise in temperature because of the internal heat generated by the functioning of these instruments.

“This rise and fall in temperature inside a satellite is a normal cyclical process. There is nothing unusual about it. But since this is the first cycle being faced by Chandrayaan, we are being extra cautious. We have decided to wait till the temperatures dip to bring the mission into the operational phase,” Mylswamy Annadurai, project director of Chandrayaan-I, told The Indian Express.

As of now, all but two of the instruments onboard have been switched on and tested. But at any given point of time, only one instrument has been operational.

Chandrayaan-I placed in lunar orbit

India's maiden moon mission --Chandrayaan-I--today entered the tricky lunar orbit after scientists successfully carried out a most critical manaoeuvre, 18 days after it was fired into outer space.
Space scientists at the Indian Space Research Organisation (ISRO) carried out the lunar orbit insertion by firing the liquid engines on board the spacecraft for 817 seconds.

"The lunar orbit insertion (LOI) began at 4:50 p.M. And lasted for 817 seconds (14 minutes)," ISRO spokesperson S Satish told PTI. The satellite has been placed in a 7,502 km X 500 km elliptical orbit around the moon, he said.

Heaving a sigh of relief, ISRO chief G Madhavan Nair said today's operation was the "most critical moment" in the mission.

"We have done it," a visbly happy Nair declared.

"For the last 20 minutes, almost all our hearts were at a standStill," Nair said from a ground centre near Bangalore.

The spacecraft, launched on October 22, had been placed in the Lunar Transfer Trajectory on November four.

The mission, orbiting the earth at a distance of 3,86,000 km, was commandeered from ISRO's Telemetry, Tracking and Command Network (ISTRAC) at Peenya on the outskirts of the city with aid from the Indian Deep Space Network (IDSN) at Byalalu.

Chandrayaan-I would now be lowered gradually and placed in a circular orbit at a distance of 100 km from the lunar surface. PTI

Chandrayaan 96 hours from moon's orbit

Chandrayaan spacecraft entered the main highway to the moon and began its 96-hour flight towards the lunar orbit.

It was the fifth and final orbit raising manoeuvre before the spacecraft entered the orbit on Saturday.

A jubilant Chandrayaan project director Mylaswamy Annadurai told TOI from Bangalore the spacecraft's 440 Newton liquid engine was fired for about two-and-a-half minutes and Chandrayaan entered the moon highway with an apogee (farthest point to earth) being 3,80,000 km.

Annadurai recalled the final moments before the spacecraft entered the moon highway also known as lunar transfer trajectory. "I was at Isro's telemetry, tracking and command network (Istrac) at Bangalore since early morning and we were going step by step very carefully. As soon as we received a signal that Chandrayaan had successfully entered the main highway to the moon, there was a jubilation in the mission control room," he said. Istrac director S K Shivakumar told TOI, "Yes, we all had a sense of satisfaction, but let me tell you that there were no clapping and embracing because the lunar orbit insertion (LOI) was still left," Shivakumar said.

He said commands are flashed to the spacecraft in the form of a digital message. "The return key in a keyboard
is hit and the message is processed by the computer and transmitted to the spacecraft. Let me assure you that the person who will be hitting this return key on Saturday for the LOI is under no pressure," he said.

Annadurai said the health of the spacecraft was being continuously monitored from the spacecraft control centre at Istrac with support from the Indian Deep Space Network antennas at Byalalu. "I am happy to say that the spacecraft is performing normally," Annadurai said.

Asked if the Chandrayaan team was nervous about the LOI on Saturday, he said the orbit raising manoeuvre on Tuesday was equally crucial. "I am hoping that the manoeuvre will go off smoothly on Saturday too," he said.

He said in all probability the LOI will occur between 5pm and 6pm on Saturday. Space scientists said this manoeuvre can be a hair-raising one because 30% of lunar missions of US and the former Soviet Union have failed because of some problems during LOI.

Chandrayaan-1 heads closer to its destination!

India’s mission towards moon took a step ahead when the fourth orbit-raising manoeuvre of Chandrayaan-1 was carried out successfully on Wednesday, October 29. The space craft was successfully raised to its fourth orbit in the morning around 7.30. This achievement has been revealed in a statement released by the Indian Space Research Organisation (ISRO) in Bangalore. ISRO stated that during the course of the operation at the spacecraft’s 440 Newton liquid engine was fired for about three minutes.

Mr. M. Annadurai-the Project Director of Chandrayaan-1 said that everything went on according to the plan. With this, the lunar spacecraft has moved closer to the moon. Now, the Chandrayaan-1 has made its entry into a more elliptical orbit whose apogee (farthest point to earth) lies at 2,67,000 km while the perigee (nearest point to earth) lies at 465 km. Thus, it implies the fact that the spacecraft’s present orbit extends more than half the way to the moon.

How Chandrayaan-1 is Raised to Higher Orbits

Chandrayaan-1 could have been fired to reach the moon, which is about 3,84,000 km from earth, in one shot. But that was not done. Instead the spacecraft is being moved towards the moon in increasingly elliptical orbits with an apogee (farthest point from the earth) increasing many times more than the perigee.

“We could have done it one shot, but there is a possibility of missing the moon,” said M. Annadurai, Project Director of Chandrayaan-1 to this Correspondent. “So we have adopted an incremental increase in the orbits’ perigee.”

That probably explains why the Indian Space Research Organisation (ISRO) has decided to settle for five increasingly elliptical orbits before Chandrayaan-1 reaches the moon’s sphere of influence. Why is the firing always undertaken at the perigee position?

Firing at perigee

“To increase the apogee, we must fire at the perigee [position]. And firing should consume less energy. So the firing is done at the perigee,” Dr. Annadurai explained.

One more reason to fire at the perigee is to ensure that the spacecraft can be tracked by 3-4 ground stations. “The spacecraft is allowed to complete one or more orbits till such time 3-4 ground stations can track it. But we will fire it at the earliest opportunity,” he said.

But not always can one assume that the firing will happen as planned. So any change in this will in turn affect the apsidal line (imaginary line that connects the apogee and perigee). This should be corrected and maintained if the rendezvous with the moon is to happen.

Increasing the apogee

And what ensures that the apogee increases many hundred kilometres after every firing while the perigee changes by only a few kilometres? “When the firing is done exactly at perigee, the velocity increases and the apogee keeps increasing. There will be no change in the perigee position,” he said.

But firing the spacecraft exactly at the perigee position is only theoretically possible. This results in a small change in the perigee altitude.

Duration of firing

“It is not an instant firing [at the perigee]. It takes a few hundred seconds to complete the firing,” he said. But great effort is however taken to centre the firing around the perigee position.

For instance, the first firing to take Chandrayaan-1 from the initial orbit to the first orbit (with an apogee of 38,000 km) took about 1060 seconds to complete. The second firing to take the spacecraft to the nearly 75,000 km apogee took 920 seconds. And the third firing to raise it to about 1,65,000 km apogee took 560 seconds.

The fourth firing to take Chandrayaan-1 to 2,67,000 km will take about 190 seconds and finally the last raise to 3,80,000 will take 150 seconds.

Though the original plan was to reach 2,00,000 km apogee in the third orbit, ISRO could only raise it to 1,65,000 km. So will that lead to any problems? “This can be made up for in the next firing,” Dr. Annadurai said.

Use of propellant

Will the change in the orbit-transfer strategy from five-and-half days to nearly a fortnight lead to increased fuel consumption and hence reduced mission life? “The amount of propellant required to fire the spacecraft to 4,00,000 km is less, whether it is done in one shot or in stages. And the propellant is used only for changing the orbits and not for orbiting around the earth,” he explained.

Orbiting around the earth is mainly through the gravitational force of the earth. But the gravitational influence of sun and moon would still play a role, though minor. Since the spacecraft goes around only for a few days in each orbit, there will not be any change in the orbits and hence the need to use propellant to correct the orbits would not arise.

But that will not be case when Chandrayaan-1 orbits the moon for two years. “There will be a need to correct the orbit once in two weeks to maintain a 100 km circular orbit,” said Dr. Annadurai.

Less energy required

While earth’s gravitational force will exist even when the spacecraft moves further and further away from the earth, the force will decrease with distance. “So firing it to the fourth and fifth orbit will require less energy,” said Dr. Annadurai. “Since some propellant is already used in the previous firings, the overall mass would come down. So the effort required to fire reduces.”

Reverse firing

Five-and-half days after the fifth firing, Chandrayaan-1 will have its rendezvous with the moon. Chandrayaan-1 will get nearer to the moon on November 8 when it reaches the 3,81,000 km apogee.

Though the moon’s influence will be predominant, the velocity of Chandrayaan-1 has to be reduced to enable the moon to capture it. Else, it can fly past the moon.

Once captured by the moon’s gravity, the velocity of the spacecraft has to be reduced to help it reach its final destination of 100 km circular orbit around the moon.

This is achieved by reversing what was done to raise its orbits.

“First, the firing is resorted at both perigee and apogee positions. And the firing takes place only after the orientation of the spacecraft is reversed — turned 180 degrees,” he said.

While the momentum of the spacecraft allows it to move in the same direction, the reverse firing helps it to reduce the velocity. The reduction in velocity is again undertaken in an incremental manner to reach the predetermined 100 km circular orbit around the moon.

Chandrayaan a wake-up call for America

WASHINGTON: From the White House to the Presidential campaign trail to the American scientific community, India’s modest Chandrayaan moon
venture, while greeted warmly, reminded the US that it was getting sloppy in maintaining its supreme lead in space expedition. ( Watch )

Democratic candidate Barack Obama, whose alert campaign staff seem to keep him abreast of any development in India (he was quick to condole the death of Field Marshal Maneckshaw even before the White House took notice), used India’s moon launch to tell Americans that they were taking their eyes off the ball.

“With India’s launch of its first unmanned lunar spacecraft following closely on the heels of China’s first spacewalk, we are reminded just how urgently the United States must revitalise its space programme if we are to remain the undisputed leader in space, science, and technology,’’ Obama said, promising to revitalise the US space programme and close the gap between the Space Shuttle’s retirement and its next-generation replacement including funding $2 billion more for Nasa.

“But more money alone is not enough,’’ he warned. “We must not only retain our space workforce so that we don’t let other countries surpass our technical capabilities; we must train new scientists and engineers for the next generation.’’ The winding down of the Space Shuttle programme and budgetary battles have constrained the US space program although President Bush stepped up to give it a boost last year.

The White House, too, pro forma hailed India’s moon mission as “encouraging’’ and “exciting.’’ But away from presidential politics and polemics, the US scientific and business community greeted the event with gusto, seeing it as an opportunity for collaboration for a greater good.

Nasa, which has two instruments on board, said data from its two instruments will contribute to its increased understanding of the lunar environment as it implements the nation’s space exploration policy, which calls for renewed robotic and human missions to the moon.

“The opportunity to fly Nasa instruments on Chandrayaan-1 undoubtedly will lead to important scientific discoveries,’’ Nasa Administrator Michael Griffin said. “This exciting collaboration represents an important next step in what we hope to be a long and mutually beneficial relationship with India in future civil space exploration.’’

Much of India’s early space ventures were undertaken with Nasa help and collaboration before the two countries fell out in the 1990s during a phase of technology denials and embargo, some of which still continues to this day.

Meanwhile, the United States India Business Council (USIBC), representing 280 of the largest US companies investing in India, also hailed the mission as the beginning of long “relationship promoting the opening of the frontier of outer space.’’

“This unique technology partnership in civil space exploration, which taps India’s highly skilled scientific expertise with American instrumentation furnished by Raytheon, beckons what we hope will be a long and mutually beneficial relationship promoting the opening of the frontier of outer space,’’ USIBC president Ron Somers said.

The Chandrayaan venture even made it to the widely watched evening network news (each of which has ten times the viewership of cable channels such as CNN and Fox) as an example of India’s progress and intent.

Space Network Guides Chandrayaan's Orbit Around Earth

The precise orbiting of India's first lunar spacecraft Chandrayaan-1 around the earth is being monitored by the telemetry, tracking and command network (Istrac) of the Indian Space Research Organisation (ISRO), a top official said in Bangalore on Friday.

"Very precise orbit determination of Chandrayaan is in progress for planning its next manoeuvre over the next two days. Health parameters of the lunar spacecraft are also being evaluated," ISRO director S. Satish told IANS.

With no orbit-raising planned on Friday, the 1380 kg spacecraft is spinning around the earth elliptically at an apogee (farthest from earth) of 37,902 km and a perigee (closest to earth) of 305 km.

"In this orbit, the spacecraft goes around the earth once in 11 hours and 5 minutes. Its health is perfectly all right and is able to send/receive signals at regular intervals from our network and ground stations," Satish said.

ISRO's deep space network (DSN) at Bylalu, about 40 km from this tech hub, is also involved in the manoeuvring exercise. It tracked the spacecraft and received signals in s and x band and sent commands in turn.

"The actual role of DSN will come into play when the spacecraft crosses 100,000 km (apogee) from the earth when its signals become feeble and time-consuming," the official said.

Chandrayaan launched Oct 22 at 6.22 am onboard the 316-tonne polar satellite launch vehicle (PSLV-C11) from the Satish Dhawan Space Centre at Sriharikota spaceport, about 80 km north of Chennai.

The spacecraft is expected to enter the lunar orbit Nov 3 when the moon will be about 500 km away (perigee).

A series of complex manoeuvres in the final phase will put Chandrayaan in the final orbit November 8, which will be about 100 km from the moon's surface.

Chandrayaan carries 11 scientific instruments, including six foreign payloads — two from the US, three from the European Space Agency (ESA) and one from Bulgaria. The remaining five are indigenously designed and developed by the various centres of the state-run ISRO.