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Two Gyro Options 18 November 2004

HSTP and STScI are considering two gyro options to extend the science mission. The first option is to transition to Two Gyro mode in summer 2005, while the second option is to transition at the start of Cycle 14 in July 2005. Both options aim to maximize time with full performance and increase the Hubble science lifetime. However, they have different implications for scheduling flexibility and program transfer. A decision needs to be made soon, contingent on a successful flight test in February.

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Two Gyro Options 18 November 2004

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  1. Two Gyro Options18 November 2004

  2. HSTP and STScI are considering gyro options to extend the science mission • Current baseline – 3 Gyro As Long As Possible (ALAP) • When next gyro fails, turn on Gyro 6 • When second gyro fails, go to Two Gyro mode • Option – 2 Gyro in summer of 2005 • Assuming no earlier failures, deliberately transition to two gyro mode at start of Cycle 14 (~ July 05) and turn off a gyro (Gyro n) • When next gyro fails, turn on Gyro 6 • When second gyro fails, turn on Gyro n • Using current reliability models, this would increase science lifetime by about 9 months

  3. 3 Gyro As Long As Possible • Maximizes time with full performance • Jitter stays low • Scheduling flexibility remains high while 3 gyros are available • Transition to Two Gyro Mode comes at an unplanned time • Scramble required to transfer programs to 2 Gyro • 3 Gyro Long Range Plan will not be optimal in 2 Gyro period • It will be impossible to transfer some programs to 2 Gyro • Estimate ~70 Orbits/week (vs. 80/week in 3 Gyro)

  4. 2 Gyro in July 05 (start of Cycle 14) • Increases Hubble science lifetime • “Uses up” Gyros at a slower rate • Transition at start of Cycle allows for advanced planning • Require Cycle 14 programs be Two Gyro compatible • Build Long Range Plan (LRP) in advance assuming Two gyro mode • Select specific transition time to manage Cycle 13 rework • Estimate ~75 Orbits/week (vs. 80/week in 3 Gyro)

  5. Science ends, 3 Gyro ALAP Science ends, 2 Gyro July 05

  6. Two Gyro Options • If we choose to deliberately go into two gyro mode early, we should inform community for Cycle 14 – requires decision soon • Such a decision would have to be contingent on a successful flight test of the full Two Gyro mode in February • STUC Input is welcome……

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