Journey of Rosetta to comet 67P

Satellite communication is the use of artificial satellites to provide communication links between various points on Earth

It plays a vital role in the global telecommunications system

Approximately 2,000 artificial satellites orbiting Earth relay analog and digital signals carrying voice, video, and data to and from one or many locations worldwide.

Satellite communication has two main components: 1. The ground segment, which consists of fixed or mobile transmission, reception, and ancillary equipment. 2. The space segment, which primarily is the satellite itself.

A typical satellite link involves the transmission or uplinking of a signal from an Earth station to a satellite.

What is Satellite Communication?

The satellite then receives and amplifies the signal and retransmits it back to Earth, where it is received and re-amplified by Earth stations and terminals.

Satellite receivers on the ground include direct-to-home (DTH) satellite equipment, mobile reception equipment in aircraft, satellite telephones, and handheld devices.

Apart from the satellites that revolve around earth serving the purpose of communication and weather updates, there are satellites/ space probes sent into the space to study about other planets and comets.

So, What’s new? (Interstellar :P)

The Picture shows a space probe which made halfway through Pluto in record time

One among such Space probe’s is Rosetta-Philae, a comet lander by European Space Agency.

Comets are the primitive building blocks of the Solar System, left over from a planet-building time when our Sun was just a disc of spinning dust and gas.

Made of ice, dust and small rocky particles, it is likely they delivered the first water to Earth and may have even seeded the planet with the building blocks for life.

Cometary dust brought back to Earth by NASA’s stardust mission contained glycine, an amino acid that is a basic part of life.

The comet and spaceship now lie 405

million kilometres from Earth, about half way between the orbits of Jupiter and Mars, rushing towards the inner Solar System at nearly 34175 miles per hour.

Comets

Rosetta- Philae comet lander Rosetta is a robotic space probe

built and launched by the European Space Agency which is performing a detailed study of comet 67P/Churyumov–Gerasimenko (67P) with both an orbiter and a lander module Philae.

On 12 November 2014, the lander achieved the first-ever controlled touchdown on a comet nucleus

Philae ' s mission was to land successfully on the surface of a comet, attach itself, and transmit data from the surface about the comet's composition.

We’re here – when Rosetta meets 67P Catch up finallyThe spacecraft Rosetta is trying to catch a comet. Today, after a decade long journey, it finally reached caught up with 67P/Churyumov-Gerasimenko

"After ten years, five months and four days travelling towards our destination, looping around the Sun five times and clocking up 6.4 billion

kilometres, we are delighted to announce finally 'we are here'," said Jean-Jacques Dordain, the director general of the European

Space Agency.

First spacecraft"Europe's Rosetta is now the first spacecraft in history to rendezvous with a comet, a major highlight in exploring our origins. The discoveries can begin."

Not a straight forward journey Rosetta has already been travelling for more than a decade after the craft was launched on March 2 2004, from Kourou, French Guiana, but its journey has been less than straightforward.

Take a sling shotThe comet is moving far faster than speeds which could ever be achieved by a spacecraft leaving Earth. So the craft has spent the time since, using the gravitational pull of the Earth and Mars to act as a sling shot and allow it to pick up acceleration.

Crucial speed: To Jupiter in a stretchWhen it reached the crucial speed in July 2011 the Rosetta was put into deep-space hibernation for the coldest, most distant leg of the journey as it travelled some 497 million miles from the Sun, close to the orbit of Jupiter as the comet headed into outer Solar System.

GLIMPSE OF THE JOURNEY

LANDING: Philae remained attached to the Rosetta spacecraft after rendezvousing with

comet 67P/Churyumov–Gerasimenko until 12 November 2014.

Nucleus : Agilkia (“Site J”) On 15 September 2014, ESA announced "Site J" on the smaller lobe of the comet as the lander's destination. Following an ESA public contest in October, Site J was renamed Agilkia in honour of Agilkia Island.

Go/NoGo Checks: A series of four Go/NoGo checks were performed 11–12 November 2014. One of the final tests before detachment from Rosetta showed that the lander's cold-gas thruster was not working correctly, but the "Go" was given anyway, as it could not be repaired.

Philae detached from Rosetta on 12 November 2014 at 08:35 UTC, landing seven hours later at 15:35.

Landing Confirmed:A confirmed landing signal was received at Earth communication stations 28 light-minutes away at 16:03 UTC

Rosetta Spacecraft Mission – Philae Comet Lander

Landing and operations on surface Soft Landing:An analysis of telemetry indicated that the landing was softer than expected, that the harpoons had not deployed upon landing, and that the thruster had not fired.

The harpoon propulsion system contained 0.3 grams of nitrocellulose, which was shown by Copenhagen Suborbitals in 2013 to be unreliable in a vacuum.

Further analysis indicated that the lander had bounced twice and landed three times; the first bounce (with a velocity of 0.38 m/s, compared to 1 m/s incoming) lasted two hours and may have been 1 km (0.62 mi) high, the second (at 0.03 m/s) lasted seven minutes.

The initial bounce was the largest in history at 1 kilometre (0.62 mi), because of the very low gravity on the comet.

Philae sits askew on all three legs, leaning on a rock in partial darkness as much as a kilometre from the first landing spot at an unknown location.

The initial battery charge was designed to power the instruments for about 60 hours. The ESA had hoped that the battery could be partially recharged by the solar panels attached to the outside of the lander, but the limited sunlight (1.5 hours per 12-hour comet day) at the landing site is inadequate to maintain Philae's activities, at least in this region of the comet's orbit

Final operations

On the morning of 14 November 2014, the battery charge was estimated to be only enough for continuing operations for the remainder of the day.

After first obtaining data from instruments whose operation did not require mechanical movement, comprising about 80% of the planned initial science observations, both the MUPUS soil penetrator and the SD2 drill were commanded to deploy. Subsequently, MUPUS data as well as COSAC and Ptolemy data were returned. A final set of CONSERT data was also downlinked towards the end of operations.

During the evening's transmission session, the lander was lifted 4 cm and rotated 35° in an attempt to position the solar panels more favorably for the future.

Philae lander detects organic molecules on surface of comet

Spacecraft beams back evidence of carbon and hydrogen that could provide clues about origins of life on Earth

Philae worked for more than 60 hours on the comet, which is more than 500m miles from Earth, before hibernating.

The Philae lander has found organic molecules, which are essential for life on the surface of the comet where it touched down last week.

Organic molecules, which are chemical compounds that contain carbon and hydrogen, form the basic building blocks of all living organisms on Earth.

They can take many forms from simple small molecules like methane gas to complex amino acids that make up proteins.

In a desperate attempt to get as much science from the lander as possible before its meagre battery reserves ran out, scientists deployed a drill to bore down into the comet surface.

But other findings from instruments on the lander, which were beamed back shortly before it powered down into a hibernation mode, suggest that the comet is largely composed of water ice that is covered in a thin layer of dust.

Contact lost:Shortly afterwards, electrical power dwindled rapidly and all instruments were forced to shut down. The downlink rate finally slowed to a trickle before coming to a stop. Contact was lost at 00:36 UTC on 15 November.

DLR's lander manager Stephan Ulamec stated:Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence. ... This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered.

Surface as hard as ice unlike expectedAnalysis of the data returned indicates that MUPUS did not penetrate much into the subsurface, which rather than being fluffy as expected is apparently as hard as ice, and that drill samples were not delivered to COSAC.

Communication loss

Potential future reawakening

Wakes up next August:Philae appears to have lost all communication capability, but it is possible that by August 2015, when the comet has moved much closer to the sun in its orbit, the lander's solar panels will receive enough illumination for ESA to reawaken it.

As the primary battery wound down "the European Space Agency decided to attempt to tilt the lander's biggest solar panel toward the sun a last-ditch maneuver that scientists believe may have paid off."

Solar panels are the source of Energy:Philae project manager Stephan Ulmanec said a few days of sun on the solar panels is all it would take to resume collecting data

References http://sci.esa.int/rosetta/

Presented by Sai Chaitanya Banala