The new number is Swift's altitude: 347 km, with 300 km as the floor

Altitude is now the mission's public number

On August 11 NASA announced that Katalyst Space had uploaded a flight software update to the LINK spacecraft. The new attitude control algorithms in that update are designed to hold the vehicle steady using the actuators it still has. The same statement carries two numbers: Swift is currently at an altitude of about 347 km, and NASA says an orbit-raising maneuver would become more difficult below an average altitude of about 300 km.^[1]

As we wrote in this column five days ago, the only publicly measurable quantity in this rescue was LINK's own spin rate; no other number showed whether the vehicle was in a state to approach Swift. This update moves the measurement. What there is to watch now is the observatory's own altitude and the floor NASA has named.^{[1], [2]}

With what the craft still has

The quietest sentence in the statement carries the most information. The new algorithms were written to maintain stability using the actuators the craft still has. That describes a workaround built around the hardware that remains. A measured reading is also available: the same wording may describe the configuration in place after the spin was slowed, and NASA does not say what failed, or whether anything did.^[1]

The order NASA gives advances step by step. Teams will perform a series of burns and maneuvers in the coming days to align LINK's orbit with Swift's, and only then comes the capture and boost attempt. Katalyst will evaluate the vehicle's performance with NASA at each phase. Each step is the condition for the next.^[1]

How long does the altitude margin hold?

In the meantime the observatory's own team has changed how Swift is operated, and NASA says the approach has reduced drag and slowed the orbital decay. The interval between the altitude and the floor therefore behaves more like a margin than a countdown. But NASA gives no decay rate, and how many days or weeks that margin runs is nowhere in public as a number. The measurement in hand gives a threshold; the measurement that would give a schedule has not been published.^[1]

A testable expectation follows. If NASA's Swift blog reports that LINK has begun its orbit-alignment burns, and the next published Swift altitude stays above 300 km, the capture attempt can proceed in the order NASA describes. The signal to watch is plain: the next altitude figure NASA publishes, and whether the alignment burns are announced. If neither arrives by the end of September, we will know no more about the mission's state than we do today.^[1]