October 29, 2007 -- The Aura spacecraft currently flies about 15.22 minutes behind Aqua in the A-Train. This position was originally dictated by the Svalbard downlink facilities' inability to acquire and download data from both Aura and Aqua within 15 minutes.
With facility upgrades, this downlink requirement no longer exists so the Aura Project is proposing to move Aura spacecraft closer to Aqua. Aura would follow Aqua by about 8 minutes along the same track after the move. Currently Aura flies a little to the west of Aqua's nadir track on the ascending node. This move requires almost no fuel and would not affect About Aura life.
The Aura spacecraft would not be moved outside the original orbit requirements for which the instruments were designed. The move will require about 4-6 months and would begin by canceling the drag make up maneuver in December. Aura would drift a few meters lower, speeding up slightly until it was within the required separation from Aqua. Then the orbit would be raised to bring Aura back into the A-Train.
This change in orbit was discussed at the October 2007 Aura science team meeting. The instrument teams have each looked at the impacts. The impacts are very minor or non existent so the Aura data products should be unaffected.
Why make such a move? There are at least two reasons. First, by moving closer to Aqua, Aura OMI will be better able to use the MODIS cloud mask to determine the clouds within the larger OMI pixels. Second, MLS limb measurements will now be nearly coincident with the Cloudsat radar and MLS & Cloudsat instruments can use this coincidence to improve their cloud ice product.