BANGALORE,
India - Five years after being formally approved and following a series of late
delays, India's first-ever planetary mission is on track to launch the morning
of Oct. 22 Local Time, with arrival in lunar orbit scheduled to occur 17 days
later.
The Chandrayaan-1
moon mission, featuring Indian, European and U.S. instruments, had been scheduled
to launch in April but suffered setbacks including late-arriving payloads and
integration issues. But officials with the Indian Space Research Organisation (ISRO),
who unveiled plans for the orbiter in 2000 with a target launch date of 2008,
are confident those issues
are behind them.
"The
spacecraft reached the launch site Sept. 30 after completing thermal vacuum,
vibration and acoustic testing in Bangalore," ISRO spokesman S. Satish said
Oct. 15. Integration with the launcher was completed Oct. 14 and at press time
the rocket was slated to be moved to the launch pad Oct. 18, he said.
"The
Chandrayaan-1 spacecraft after successfully completing [thermal vacuum],
vibration and acoustic tests, has reached the launch site," ISRO spokesman S.
Satish told SPACE.com sister publication Space News Oct. 8. "All
the operations are going on satisfactorily."
If all goes
well, Chandrayaan - which means moon vehicle in Hindi - will join two other spacecraft
that reached lunar orbit roughly one year ago: Japan's
large Kaguya, or Selene, mission, which launched in September 2007, and China's
Chang'e 1, which launched in October 2007. NASA's Lunar Reconnaissance Orbiter
is slated to launch in February, meaning that four spacecraft, each built by a
different country, could be in lunar orbit simultaneously.
Built at a
cost to ISRO of some $87 million, the fully fueled Chandrayaan-1 will weigh
2,874 pounds (1,304 kg) when it lifts off from the Satish Dhawan Space Centre
on Sriharikota Island off India's east coast. After a countdown lasting 52 hours,
the probe will lift off tomorrow at 6:20 a.m. Local Time (Tuesday evening Oct.
21 EDT) aboard a modified version of ISRO's Polar Satellite Launch Vehicle, or
PSLV.
The probe
will be India's first to leave Earth orbit, something that will be accomplished
not by a direct transfer typical of lunar missions but rather through a series
of Earth orbit-raising maneuvers. In direct transfer missions, a spacecraft is
placed into a parking orbit around Earth before on board propulsion systems
give it a substantial velocity boost to place it into a lunar transfer orbit
with an apogee of 238,550 miles (384,400 km) - roughly the moon's average distance
from the Earth.
"Direct
transfer would have required an additional stage to PSLV," said V. Adimurthy, a
scientist at ISRO's Vikram Space Science Centre, where the rocket was built.
Satish said
the PSLV will inject Chandrayaan-1 into an elliptical orbit around the Earth
with a perigee of 155 miles (250 km) and an apogee of 14,291 miles (23,000 km).
The spacecraft will reach lunar orbit by firing its liquid-fueled apogee motor
several times. The first firing will put the spacecraft in a 186- by
22,990-mile (300- by 37,000-km) Earth orbit. Successive firings will raise the
apogee to 45,360 miles (73,000 km) and then to the lunar transfer trajectory
orbit of 186 by 240,470 miles (300 by 387,000 km).
"It takes
about 11 days after launch to establish the lunar transfer trajectory," Satish
said.
Further
firings will insert Chandrayaan-1 into a 310- by 3,106-mile (500- by 5,000-km)
orbit around the moon. The orbit will then will be lowered to 62 by 3,106 miles
(100 by 5,000 km) and finally to the desired 62-mile (100-km) circular
orbit, which will take the spacecraft over the Moon's poles once every 118
minutes.
"If the
launch takes place on Oct. 22, the spacecraft is expected to enter the
100-kilometer lunar orbit on Nov. 8," Satish said.
The
Chandrayaan-1 spacecraft itself is relatively small, measuring about 5 feet (1.5
meters) on a side with a dry mass of only 1,153 pounds (523 kg). It
carries 11 scientific payloads, including six provided by other nations: two from
the United States, and one each from Britain, Sweden, Germany and Bulgaria.
"The real
challenge was in accommodating different payloads in specific locations and
orientations in a small spacecraft," Mylswamy Annadurai, Chandrayaan-1 project
director, told Space News.
The
Indian-built payloads are: the Terrain Mapping Camera; Lunar Laser Ranging
Instrument; Hyperspectral Imager; High Energy X-Ray Spectrometer; and the Moon
Impact Probe.
The 64-pound
(29-kg) impact probe will be released from the orbiter over a selected
site once the spacecraft enters its final orbit, Satish said. During its 18-minute
descent, the impact probe - with India's national flag painted on its shell - will
take images of the lunar surface. Its impact will kick up a cloud of dust that
will be observed and analyzed by the instruments on the orbiter.
Among the
international payloads, India collaborated on two: the X-ray Fluorescence
Spectrometer with Britain's Rutherford Appleton Laboratory; and the Sub-keV
Atom Reflecting Analyzer with the Swedish Institute of Space Physics. The other
international payloads are: a Mini Synthetic Aperture Radar built by the Johns Hopkins
University's Applied Physics Laboratory of Laurel, Md.; Moon Mineralogical
Mapper supplied by NASA's Jet Propulsion Laboratory and Brown University; Near
Infrared Spectrometer from Germany's Max Planck Institute; and Radiation Dose
Monitor supplied by the Bulgarian Academy of Sciences.
In addition
to mapping lunar surface features and topography, the instrument suite will
study the Moon's elemental and mineralogical composition - in part by measuring
reflectance from solar flares that are expected to rise in frequency and
intensity over the next few years. "Water-ice, if present, can be detected by
several of these instruments," ISRO said on its Web site.
In response
to questions, Narendra Bhandari, who until recently headed ISRO's planetary exploration
division, listed four main Chandrayaan-1 objectives:
- Study how
volatile elements and compounds - possibly including water - get
transported to the poles from the hot lunar surface during the day.
- Produce a
digital elevation map with 5-meter resolution both vertically and
horizontally. This will enable scientists to select potential sites for a
future base.
- Produce
chemical and mineral maps of the moon. The mineral spectrometer will
measure signals up to 3 microns in the near-infra red portion of the electromagnetic
spectrum - data that has not previously been collected - giving scientists
new information about water and possible organic compounds at the poles.
- Map
subsurface features on the Moon using a synthetic aperture radar.
"Simultaneous
photo-geological, mineralogical, and chemical mapping will enable us to
identify different geological units, which will test the early evolutionary history
of the Moon," Bhandari said.
He added
that the simultaneous presence of four Moon probes will enable coordinated
study. For example, he said, one mission may benefit from data collected by another;
or one probe could observe as another crashes into the surface after completing
its mission.
advertisement
