The maneuver plan is shown in Table F-2. Of the three deep space maneuvers (DSM’s), only the first is deterministic. This maneuver targets the EGA in January, 2009. Other DSM’s adjust the arrival time at Tempel 1. Ranges of favorable locations for DSMs (2 and 3) are indicated. Their exact location will be optimized during the mission.
Table F-2. Maneuver plan targets EGA and Tempel 1 encounter with few maneuvers
|Maneuver||Epoch||Comment||Execution Date (UTC)|
|DSM1||Entry + 603d||EGA Targeting||9/19/07|
|DSM1_CU||DSM1 + 30d||Cleanup||10/19/07|
|EGA2||E - 10d||EGA Targeting||1/5/09|
|EGA2a||E - 1d||EGA Targeting||1/13/09|
|DSM2||T1 - 1y||Arrival Time Adjust||2/12/10|
|DSM2_CU||DSM2 + 30d||Cleanup||3/14/10|
|T1 (DSM3)||T1-30d||T1 Targeting||1/15/11|
|T2||T1 - 10d||T1 Targeting||2/4/11|
|T3||T1 - 2d||T1 Targeting||2/12/11|
|T4||T1 - 18h||T1 Targeting||2/14/11|
|T5||T1 - 6h||T1 Targeting (Contingency)||2/14/11|
The Stardust navigation team has chosen to place the closest approach point 40° southward of the direction to the Sun, at a longitude that offers the most favorable viewing opportunity of the Deep Impact crater at closest approach. Periodically, reevaluate the aimpoint during the mission, taking into account the most recent information available about the predicted uncertainty of the comet’s rotation state at encounter, until the time shortly before DSM2 (deep space maneuver) at which a selection of a final aimpoint for targeting.
Controlling the arrival time to target our chosen aimpoint is the greatest mission design challenge of Stardust-NExT. In order to successfully control the arrival time as discussed above, two conditions must be met: (1) we must be able to predict the rotation rate and rotational state of the comet with sufficient accuracy to reliably compute the right arrival time, and (2) we must have sufficient DV onboard to change the arrival time as needed.