Rosetta's next orbital correction manoeuvre (OCM) is taking place tonight. The thruster burn began at 17:59 CET (spacecraft time) and will run until shortly after midnight (371 mins total). The planned change in speed is 274 m/s with respect to the Sun. Like last night, the Rosetta teams at ESOC will be on shift until late!
Some bits of info collected from around ESOC earlier today on the Rosetta burn last night:
First - An update from the Rosetta flight control team: yesterday's burn went according to plan! The team noted a very slight over performance - meaning that the thrusters provided more of a boost than planned but still well within the expected range (more on that below). For the flight control & flight dynamics teams, the last shift ended at 04:30 CET this morning (just after the burn ended).
Next - the detailed burn schedule is posted below (click on the 'Full story' link), sent in by Roberto Porta, one of the Rosetta Spacecraft Operations Engineers at ESOC. Note that we'll wait to do any further blog updates until we get the final results after the last slot, now booked for 23 January.
Finally - we received a note from Trevor Morley, the team lead for flight dynamics support for Rosetta. Trevor wrote:
Preliminary assessment of last night's manoeuvre based on Doppler data indicates that the velocity change was about 1 m/s more than the planned 300 m/s. Such an error is well within the expected performance accuracy and the accumulation of such errors over the first four legs of the manoeuvre will be compensated for by an eventual re-optimisation of the 5th and final leg (an 'orbit trim'). This re-optimisation will be based upon an accurate reconstruction of the orbit for which purpose both ESA and NASA delta-DOR measurements will be made in addition to routine Doppler and range measurements.'Delta-DOR' refers to the ultra-accurate position determination technique used by both ESA and NASA. Delta-DOR uses two widely separated antennas to simultaneously track a transmitting probe in order to measure the time difference ('delay time') between signals arriving at the two stations. The technique of measuring this delay is named Differential One-way Range (DOR). More details via the ESTRACK pages in the ESA web site. -- Daniel
Rosetta orbital correction manoeuvre activity January 2011 (all times UTC = CET - 1)
18 Jan - planned magnitude 274 m/s - Expected duration 371 mins
18:59:31 Start OCM
01:13:00 End of OCM
21 January - planned magnitude 120 m/s - Expected duration 171 mins
18:49:07 Start OCM
21:40:00 End of OCM
23 January - planned magnitude 78.2 m/s - Expected duration 118 mins
18:42:05 Start OCM
20:39:05 End of OCM
(Further slots are available as needed)
Delta-DOR tracking campaigns to precisely determine Rosetta's position using ESA's 35m deep-space station at New Norcia, Australia, and NASA Deep Space Network stations at Goldstone, California, and Canberra, Australia, will take place during the second half of January and the second half of February.