Exploring the universe through Rosetta

Comets are among the primitive particles of the universe that can unveil the secrets of the universe and help us understand the origin of the universe. The European Space Agency has planned to study the comet comet 67P/ Churyumov–Gerasimenko passing by the earth. ESA built a robotic space probe named Rosetta with a lander module named Philae. It was launched on March 2, 2004 on an Ariane 5 rocket and reached the comet on August 6, 2014, becoming the first spacecraft to orbit a comet.

Rosetta spacecraft:

• It is one of ESA's Horizon 2000 cornerstone missions
• The spacecraft consists of the Rosetta orbiter, which features 12 instruments, and the Philae lander, with nine additional instruments
• The probe is named after the Rosetta stone, a stele of Egyptian origin featuring a decree in three scripts
• The lander is named after the Philae obelisk, which bears a bilingual Greek and Egyptian hieroglyphic inscription
• A comparison of its hieroglyphs with those on the Rosetta stone catalysed the deciphering of the Egyptian writing system. Similarly, it is hoped that these spacecraft will result in better understanding of comets and the early Solar System
• Electrical power for the spacecraft comes from two solar arrays totaling 64 square metres

Rosetta Mission:

• Rosetta was launched on August 6, 2014 and performed two asteroid flyby missions on its way to the comet
• On its way to comet 67P comet, Rosetta passed through the main asteroid belt and made the first European close encounter with several of these primitive objects
• Rosetta was the first spacecraft to fly close to Jupiter's orbit using solar cells as its main power source
• It is also the first spacecraft to fly alongside a comet as it heads towards the inner solar system and examines at close proximity how a frozen comet is transformed by the warmth of the sun
• On January 20, 2014, Rosetta was taken out of a 31-month hibernation mode as it approached the comet
• It successfully made the first soft landing on a comet nucleus when it touched down on 67P on November 12, 2014
• The spacecraft is controlled from the European Space Operations Centre (ESOC)
• The planning for the operation of the scientific payload, together with the data retrieval, calibration, archiving and distribution, is performed from the European Space Astronomy Centre (ESAC).

Orbiting 67P comet:

• In August 2014, Rosetta rendezvoused with the comet 67P and commenced a series of maneuvers that took it on two successive triangular paths, averaging 100 and 50 kilometers from the nucleus, whose segments are hyperbolic escape trajectories alternating with thruster burns
• After closing to within about 30 km from the comet on September 10, the spacecraft entered actual orbit about it.
• The orbiter mapped the comet in anticipation of detaching its lander
• By August 25, 2014, five potential landing sites had been determined, but the head of the comet was finalised as destination for Philae lander

Philae Lander:

• Philae was detached from Rosetta and landed on the comet on November 12, 2014 which initially has lost its communication with ESA and then started transmitting after two hours.
• After landing on the comet, the Philae was scheduled to commence its science mission
• It was meant to study the characterisation of the nucleus and determine the chemical compounds present, including amino acid enantiomers
• It was also meant to study comet activities and developments over time.

Investigation of comet nucleus

Nucleus of the comet was done by three spectroscopes, one microwave radio antenna and radar.

Alice: Alice is an ultraviolet spectrograph which will search for and quantify the noble gas content in the comet nucleus, from which the temperature during the comet creation could be estimated.

OSIRIS: (Optical, Spectroscopic, and Infrared Remote Imaging System) is a narrow angle lens camera which will click images of the comet.

VIRTIS: (Visible and Infrared Thermal Imaging Spectrometer) is an IR spectrometer which will be able to make pictures of the nucleus in the IR and also search for IR spectra of molecules in the coma

MIRO: (Microwave Instrument for the Rosetta Orbiter), it checks for the volatile substances like water, ammonia and carbon dioxide which usually be detected by microwave emissions.

CONSERT: (Comet Nucleus Sounding Experiment by Radiowave Transmission). It will provide information about the deep interior of the comet using radar. The radar will perform tomography of the nucleus by measuring electromagnetic wave propagation between the Philae lander and the Rosetta orbiter through the comet nucleus. This allows it to determine the comet's internal structure and deduce information on its composition.

RSI: (Radio Science Investigation) RSI makes use of the probe's communication system for physical investigation of the nucleus and the inner coma of the comet.

Investigations:

• One of the first discoveries was that the magnetic field of 67P oscillates at 40–50 millihertz
• Scientists modified the signal by speeding it up by 10,000 times so that people can hear it. While a natural phenomenon, it has been described as a song
• On December 10, 2014, scientists reported that the composition of water vapour from comet 67P, as determined by the Rosetta spacecraft, is substantially different from that found on Earth. That is, the ratio of deuterium to hydrogen in the water from the comet was determined to be three times that found for terrestrial water
• This makes it very unlikely that water found on Earth came from comets such as comet 67P according to the scientists
• On January 22, 2015, NASA reported that, between June and August 2014, the comet released increasing amounts of water vapor, up to tenfold.