Science For You

[Perfection]

Moon : Earth's only planet, the neighbor

The average distance from the Earth to the Moon is 384,399 km, which is about 30 times the diameter of the Earth. The Moon is about one-third the size of the Earth and has a diameter of 3,474 km. It is the fifth largest moon in the Solar System behind Ganymede, Titan, Callisto and Io. The Moon makes one complete orbit about the Earth every 27.3 days, and the
periodic variations in the geometry of the Earth-Moon-Sun system are responsible for the lunar phases that repeat every 29.5 days. The gravitational attraction of the Moon is responsible for the tides on Earth.

The Moon is the only celestial body on which human beings have orbited and landed. The first man-made object to escape Earth's gravity and pass near the Moon was the Soviet Union's Luna 1, the first man-made object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The first spacecraft to perform a successful lunar soft landing was Luna 9 and the first unmanned vehicle to orbit the Moon was Luna 10, both in 1966. The United States' Apollo program achieved the first (and only) manned missions to the Moon, culminating in 6 landings between 1969 and 1972.

[Perfection]

The Apollo 11 mission was the first manned mission to land on the Moon. It was the fifth human spaceflight of Project Apollo and the third human voyage to the Moon. It was also the second all-veteran crew in manned spaceflight history. Launched on July 16, 1969, it carried Commander Neil Alden Armstrong, Command Module Pilot Michael Collins and Lunar Module Pilot Edwin Eugene 'Buzz' Aldrin, Jr. On July 20, Armstrong and Aldrin became the first humans to land on the Moon, while Collins orbited above.

The mission fulfilled President John F. Kennedy's goal of reaching the moon by the end of the 1960s, which he expressed during a speech given on September 12, 1962 at Rice University Stadium in Houston, Texas.

[Perfection]

India's first Moon mission : Chandrayan-1 (unmanned lunar mission)

Government of India approved ISRO's proposal (Indian Space Research Organisation) for Chandrayaan-1 in November 2003. Chardrayaan is meant to probe the physical characteristics of the lunar surface in greater depth than previous missions by other nations. The main objective of the mission is to carry out high resolution mapping of topographic features in 3D, distribution of various minerals and elemental chemical species including radioactive nuclides covering the entire lunar surface using a set of remote sensing payloads. The new set of data would help in unravelling mysteries about the origin and evolution of solar system in general and that of the moon in particular.

Specific areas of study

* High resolution mineralogical and chemical imaging of permanently shadowed north and south polar regions
* Search for surface or sub-surface water-ice on the moon, specially at lunar pole
* Identification of chemical end members of lunar high land rocks
* Chemical stratigraphy of lunar crust by remote sensing of central upland of large lunar craters, South Pole Aitken Region (SPAR) etc., where interior material may be expected
* To map the height variation of the lunar surface features along the satellite track
* Observation of X-ray spectrum greater than 10 keV and stereographic coverage of most of the moon's surface with 5 m resolution, to provide new insights in understanding the moon's origin and evolution

[Perfection]

Chardrayaan-1 is the first Indian Mission to the Moon devoted to high-resolution remote sensing of the lunar surface features in visible, near infrared, X-ray and low energy gamma ray regions. This will be accomplished using several payloads already selected for the mission.

On 22 Oct 2008, India become a member of the Moon club of USA, Russia, Japan, China and European Space Agency. The Moon mission costs Rs Rs 400 Crores.

Satish Dhawan Space Centre (SDSC) at Sriharikota

It was originally called Sriharikota Range (SHAR) and renamed to its present name in 2002 after the death of ISRO's former chairman Satish Dhawan. The centre become operational with the launching of three Rohini rockets in October 1971. The SHAR facility now consists of two launch pads, with the second built recently. The second launch pad was used for launches beginning in 2005 and is a universal launch pad, accommodating all of the launch vehicles used by ISRO. The two launch pads will allow multiple launches in a single year, which was not possible earlier.

The 44.4 m high 316 ton (Polar Satellite Launch Vehicle) PSLV C11 four stage Solid-liquid propellent rocket was fired from Satish Dhawan Space Centre (SDSC) at Sriharikota in Andhra Pradesh on 22 Oct 2008 at 0622 h IST(80 km north of Chennai). The rocket achieved a speed of more than 7.2 km/s (Orbital Velocity) with the help of powerful strapon motors. The strapon motors used 12 ton of solid propellent and within 18 minutes all the four stages were used up and detatched.

[Perfection]

Polar Satellite Launch Vehicle (PSLV)

The Indian Space Research Organisation (ISRO) built its Polar Satellite Launch Vehicle (PSLV) in the early 90s. The 45 m tall PSLV with a lift-off mass of 295 tonne, had its maiden success on October 15, 1994 when it launched India's IRS-P2 remote sensing satellite into a Polar Sun Synchronous Orbit (SSO) of 820 km.

Between 1996 and 2005, it has launched six more Indian Remote Sensing satellites as well as HAMSAT, a micro satellite built by ISRO for amateur radio communications into polar SSOs, one Indian meteorological satellite into Geosynchronous Transfer Orbit (GTO).

PSLV has also launched four satellites from abroad (TUBSAT and DLR-Bird from Germany, Proba from Belgium and KITSAT from Republic of Korea) as piggyback payloads into polar SSOs. PSLV has emerged as ISRO's workhorse launch vehicle and proved its reliability and versatility by scoring eight consecutive successes between 1994-2005 periods in launching multiple payloads to both SSO as well as GTO.

On January 10, 2007, the PSLV-C7 carried four satellites - the 680 kg Indian remote sensing satellite CARTOSAT-2, the 550 kg Space Capsule Recovery Equipment (SRE-1), Indonesia's LAPAN-TUBSAT (60 kg) and Argentina's 6 kg nanosatellite called NANO PEHUENSAT-1 into orbit.

Considering the maturity of Polar Satellite Launch Vehicle (PSLV) demonstrated through PSLV-C4/KALPANA-1 mission, PSLV is chosen for the first lunar mission. The upgraded version of PSLV viz., PSLV-XL which has a liftoff weight of 316 tonnes, will be used to inject 1304 kg mass spacecraft at 240 x 24,000 km orbit and the corresponding spacecraft mass is 590 kg when the target lunar orbit of 100 km is achieved.

[Perfection]

Orbit 1 : The Moon probe (11 instruments weighing 1380 kg) was placed in an oblate orbit of earth after covering 400,000 km. In the orbit, the Moon probe will come 255 km closer to earth and the farthest distance will be 22,860 km.

Orbit 2 : By firing small rockets, the orbit will be changed. The Moon probe's farthest distance from earth will be increased to 22,860 km.

Orbit 3 : By firing 440 Newton liquid engine rockets for 18 minutes, the orbit is changed (24 Oct 08). The Moon probe's farthest distance from earth (apogie) will be increased to 37,900 km. The period of rotation of the Moon probe in orbit is 11 hours.

Orbit 4 : The Moon probe's farthest distance from earth will be increased to 73,000 km.

Orbit 5 : The Moon probe's farthest distance from earth will be increased to 387,000 km.

Orbit 6 : By firing small rockets, the orbit will be changed. Now the Moon probe will revolve around Moon. In the first Moon's orbit with an apogie of 5000 km.

Orbit 6 : In the second Moon's orbit with an apogie (farthest distance) of 5000 km and a perigee of 100 km (closest distance).

Orbit 7 : Finally the Moon probe will move in an oblate orbit having an apogie of 100 km. This orbit will be achieved on 8 Nov.

[Perfection]

Spacecraft specifications

* Cuboid in shape of approximately 1.5 m side.
* Weighing 1304 kg at launch and 590 kg at lunar orbit.
* Accommodates eleven science payloads.
* 3-axis stabilized spacecraft using two star sensors, gyros and four reaction wheels.
* The power generation would be through a canted single-sided solar array to provide required power during all phases of the mission. This deployable solar array consisting of a single panel generates 700 W of peak power. Solar array along with yoke would be stowed on the south deck of the spacecraft in the launch phase. During eclipse spacecraft will be powered by Lithium ion (Li-Ion) batteries.
* After deployment the solar panel plane is canted by 30 degree to the spacecraft pitch axis.
* The spacecraft employs a X-band, 0.7 m diameter parabolic antenna for payload data transmission. The antenna employs a dual gimbal mechanism to track the earth station when the spacecraft is in lunar orbit.
* The spacecraft uses a bipropellant integrated propulsion system to reach lunar orbit as well as orbit and attitude maintenance while orbiting the moon.
* The propulsion system carries required propellant for a mission life of 2 years, with adequate margin.
* The Telemetry, Tracking & Command (TTC) communication is in S-band frequency.
* The scientific payload data transmission is in X-band frequency.
* The spacecraft has three Solid State Recorders (SSRs) on board to record data from various payloads. SSR-1 will store science payload data and has capability of storing 32 Gb data. SSR-2 will store science payload data along with spacecraft attitude information (gyro and star sensor), satellite house keeping and other auxiliary data. The storing capacity of SSR-2 is 8 Gb. M3 (Moon Mineralogy Mapper) payload has an independent SSR with 10 Gb capacity.