No. 125 - Earth swingby clean-up manoeuvre
02 December 2009 11:55
Report for Period 14 November to 27 November 2009
The reporting period covers the first two weeks after Rosetta's third Earth swingby. The scientific observations linked to the Earth swingby phase were concluded successfully. Fine orbit determination computations were conducted after the Earth swingby to verify Rosetta was on the desired outbound trajectory. These indicated that a clean-up trajectory correction manoeuvre (TCM) was necessary to correct for a small inaccuracy. The clean-up TCM, with a delta-V of about 58 cm/s, was successfully performed on 23 November.
During the second half of the reporting period the bulk of the activities required for the refresh of all spacecraft Electrically Erasable Programmable Read Only Memory (EEPROM) were conducted. This included refreshing the EEPROMs of the four processor modules (PM) of Rosetta's on-board Data Management System.
Mission operations have been mainly conducted with support of the ESA New Norcia (NNO) ground station. In addition several tracking passes with the NASA DSN ground stations Goldstone (DSS-24) and Madrid (DSS-54) were scheduled.
At the end of the reporting period (DoY 331) Rosetta was at 11 million km from Earth (0.073 AU) and the one-way signal travel time was 37 seconds. The distance to the Sun was 146.87 million km (0.982 AU).
On 23 November 2009 Rosetta was at the perihelion of its current orbit, 146.6 million km (0.98 AU) from the Sun. Rosetta will never come as close to the Sun again; two deep space manoeuvres in 2011 and 2014 will synchronize Rosetta's orbit with that of comet 67P/Churyumov-Gerasimenko, whose orbit around the Sun lies well beyond that of the Earth.
Earth swingby navigation campaign
Based on orbit determination results obtained using the radiometric data starting with the New Norcia pass on 8 November and ending with the New Norcia pass that finished early on 18 November, the following summary can be made of the Earth swingby:
With the successful execution of the clean-up TCM on 23 November, the Earth swingby phase of the Rosetta mission operations is now almost completed. Few minor spacecraft configuration changes will mark the transition into the next cruise phase that will lead to the encounter with asteroid Lutetia in July 2010.
The upcoming period will see the preparation for the test of the Deep Space Hibernation Mode. This test is planned between 20 and 27 January 2010 and is needed to validate the procedure planned for June-July 2011, when Rosetta will go into deep space hibernation for a period of two and a half years.