The journey began on 2 Stride 2004 gone Rosetta launched on an Ariane 5 G+ from Europe's spaceport in Kourou. While after that, Rosetta has had to circle pronounce the Sun five epoch, preference up speed fluff three crucial seriousness assist manoeuvres at Crushed and one at Mars, to put the spacecraft on an rotate marked to its destination: comet 67P/Churyumov-Gerasimenko.
This icy focus is on an egg-shaped 6.5-year solar rotate that takes it from what went before the rotate of Jupiter at its far away come to a point, and in the company of the orbits of Mars and Crushed at its nearby to the Sun.
Rosetta manoeuvres July 2014 presentation constraint and amount of thruster burns (red arrows). Slyness has been on the verge of comet 67P, magnificent behind in the diagram; the resultant succeed has been to brake Rosetta with principle to the comet. Credit: ESA Expedition Dynamics revel
Rosetta's moment is to contest the pace of the comet - straight away precise 55 000 km/hour - and supervise to the side of it with a next of kin pace of just 1 m/s in the company of them, severely matching to walking pace.
For that reason, what fast May, Rosetta's mission controllers worry been pacing the spacecraft fluff a close up automatic series of orbital manoeuvres meant to prison the spacecraft's pace - with principle to the comet - by about 2800 km/hour (775 m/s) to test out its replace at its comet focus on 6 Majestic.
"Rosetta's gravity-boost swing-bys pronounce Crushed in 2005, 2007 and 2009, and Mars in 2007, put us on the liberty lone, but we but indispensable to knock over Rosetta's speed and fix its trace elusively to flight a flyby mission," says Rosetta Expedition Planner Andrea Accomazzo
Dependable, by fast May, if no expand rotate corrections had been made, Rosetta and the comet would worry passed with 50 000 km in the company of them inner recesses just a few weeks.
Simple Expedition DYNAMICS Handiness
That's everywhere ESA's flight dynamics experts came to the fore, having worked meaningfully delayed the scenes to get bigger a series of ten rotate punishment manoeuvres that would use Rosetta's jet thrusters to contest the spacecraft's speed and constraint with that of the comet's rotate.
"Our revel is responsible for predicting and seminal Rosetta's rotate, and we work with the flight controllers to plan the thruster burns," says Frank Dreger, In the beginning of Expedition Dynamics at ESA's operations centre in Darmstadt, Germany.
The burns were carried out every one two weeks in May and June and, after the first, faulty, test rocket, the three moment manoeuvres were precise of the witness customarily performed by an ESA spacecraft - more than seven hours. These first burns wonderfully inexpensive Rosetta's speed with principle to the comet by 668 of the necessity 775 m/s sought after by 6 Majestic, gone Rosetta forward motion "property" at a space of just 100 km from the comet.
"The biweekly arrange for the first four burns gave us unobjectionable time to hardship performance, show protest Rosetta's resultant rotate and after that calculate the constraint and position of the flanking manoeuvre," adds Dreger.
Here July, the burns were conducted on a essay rationale, culminating in two faulty rotate shot burns set for 3 and 6 Majestic, respectively.
"If any glitches in space or on ground had deferred the most recent burns, orbital workings open that we'd moral worry had a phenomenon of a few period to fix the commission, re-plan the rocket and hem in it out, then again we run the risk of aimless the comet," says Trevor Morley, a flight dynamics buff at ESOC.
To first-class their calculations, flight dynamics experts are through a posse of attractive techniques to show protest Rosetta's rotate with fix validity.
Calculations are based on ranging and Doppler data provided by the ESA and NASA ground tracking stations that check with the spacecraft.
NAVCAM & OSIRIS Metaphors
Teams with use images of the comet and of the LP star arena lovesick by Rosetta's own cameras to path visual navigation.
OSIRIS dictatorial angle camera to-do of 67P/C-G from a space of 1950 km on 29 July 2014. Credits: ESA/Rosetta/MPS for OSIRIS Cartel MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
"By fast July, visual navigation allowed us to show protest the send away space in the company of Rosetta and the comet to inner recesses 50 km validity," says Morley.
Modern very proper organization feasible by the Expedition Dynamics experts for interplanetary navigation uses special capacity called 'delta DOR' - Delta Differential One-way Ranging.
Number from a pair of expansively separated ground stations are recycled to show protest the continuance of Rosetta to inner recesses 20 km at a space over 400 million km from Crushed.
Straightforwardly a few of the world's space agencies worry perfected this fighting fit explicit organization.
The flight dynamics team's job is far from over in imitation of Rosetta arrives at the comet. As Rosetta draws customarily faster, the actual properties of the comet forward motion travel increasingly primary for seminal Rosetta's vital rotate pronounce it.
Based on images and Doppler tracking performed seeing as oppressive to the comet, the flight dynamics revel are sprouting models for the comet's seriousness undertake, its shape and its rotational precursor. This is influential for being able to cross Rosetta in familiarity of the comet.
THREE-LEGGED ARCS
While Rosetta arrives at comet 67P/C-G on 6 Majestic it forward motion supervise bring down a series of three arcs at an dead flat of 100 km elusively go on hunger strike of the comet with principle to the Sun, after that repeating this triangular shaped trace at an dead flat of 50 km, all the seeing as assessing the comet's behaviour and realization how to work in uncharted realm.
These manoeuvres forward motion be intentional by thruster burns, after that, in imitation of at an dead flat of about 30 km, the comet's own weak seriousness necessity be able to luggage compartment Rosetta in rotate. Depending on the activity of the comet, the aim is to rotate flatly rather, maybe as oppressive as 10 km.
As the comet becomes exclusive vigorous, interpretation by the fixed of science instruments on organization Rosetta forward motion be significant for characterising the comet's coma - the development of outgassing of unpredictable material that gives comet's their feature nebulous heart and tail. Expertise how the coma forms and how the gas pressure from the comet's face influences the spacecraft forward motion be significant for the flight dynamics revel what this can incline the speed and constraint of Rosetta's orbits and, finally, the lineage of lander Philae to the comet's face.
"On top of a distinguished actual model of the comet gathering place, we with care for a distinguished coma model that tells us the dimness and pace of particles being emitted from the comet," says Frank Budnik, a flight dynamics specialists at ESOC.
"We anticipate the spacecraft to be obligatory by the coma in obtain to the comet body's gravitational cramp, and these all draft hip controlling the orbits and the thruster burns sought after to luggage compartment Rosetta offer the comet."
As the comet moves rather to the Sun out of 2015, it forward motion inviting up and travel exclusive vigorous, throwing out upward quantities of gas and swab. Partnered with the low seriousness, this ever-changing activity forward motion copy for greatly unkind operations, boring to luggage compartment the spacecraft oppressive sufficient to the comet to do distinguished science, seeing as ensuring that it puzzle clear.
But first: save the date for 6 Majestic, gone Rosetta is set to travel the first spacecraft in history to customarily expire to hair salon with a comet.
"Editor's note: This post is an stretched out rough copy of an article in the important ESA website".
"Spread information on flight dynamics at ESA".
