OMI Life Limited Items Usage and Budget

The OMI instrument is equipped with a number of life limited items (LLIs) for which a maximum usage budget has been predefined. These items include:
  • The Sun Aperture Mechanism (SAM): number of cycles
  • The Diffuser Mechanism (DifM): number of cycles
  • The Folding Mirror Mechanism (FMM): number of cycles
  • The number of burn seconds for the White Light Source (WLS)
One cycle is a movement back and forth.
The LED is not a life limited item.
The in-flight operations scenario uses predefined orbit types (daily; weekly 1,2,3; monthly 1,2,3) that employ the life limited items for a specific number of times or seconds.
Four phases are distinguished:
  • The pre-launch period.
  • The Launch and Early Operations Phase (LEOP) that lasted roughly from 15 July 2004 to 1 October 2004. During this phase the in-flight operations were not nominal.
  • The in-flight phase(s) for anomaly investigations.
  • The in-flight phase after LEOP, excluding anomaly investigations.
The tables below show the life limited items status split up according to the above descriptions.

In-flight Life-Limited Item Usage per Orbit Type
Orbit Type Number of orbits SAM Cycles DifM Cycles FMM Cycles WLS Seconds
Daily 2358 2358 2358 7074 0
Monthly 1 81 81 81 320 0
Monthly 2 79 79 158 237 12309
Monthly 3 79 0 0 79 0
Weekly 1 315 315 315 630 0
Weekly 2 316 316 632 1264 22726
Weekly 3 394 0 394 1576 8636
Total - 3149 3938 11180 43671

Life-Limited Item Usage for Specific Events / Periods
Event / Period SAM Cycles DifM Cycles FMM Cycles WLS Seconds
On-ground Testing and Analysis 2524 2131 2157 43200
Launch and Early Operations Phase (LEOP) 142 188 616 3534
In-flight Anomaly Investigation / Others 0 0 44 2492
Total 2666 2319 2817 49226

Total Life-Limited Item Usage and Budget
Description SAM Cycles DifM Cycles FMM Cycles WLS Seconds
Total Used 5815 6257 13997 92897
Budget 30916 30916 30916 216000
Budget Spent 18.81% 20.24% 45.27% 43.01%