6 June 1994
The actual time-line for IUE observations is not yet set, as of the date above. The following summarizes the allocations and plans as far as they are known.
IUE is operated jointly by NASA, which allocates 2/3 of the observing time, and by ESA and SERC, which allocate 1/3 of the observing time. Observing is scheduled in 8-hour shifts and the observatory normally operates 24 hours per day because it is in a high, geosynchronous orbit. Twice a year, there is a period of a couple of weeks when the orbit of IUE takes it through Earth's shadow once per day. The satellite can not be operated while it is in Earth's shadows since there is not enough power from batteries without any charging from the solar panels. Unfortunately, the 'summer shadow season' includes the impact week. This means that IUE will lose several hours of operation each day during the impact week. Usually in July the US shifts would start at 0300 and 1100 UT while the ESA shift would start at 1900 UT. These times will be modified during the shadow season but the details are not yet decided.
On the US side, three PIs were allocated a total of 14 US-1 shifts and 16 US-2 shifts. Walt Harris (U. Michigan), Tim Livengood (GSFC), and Melissa McGrath (STScI) will be studying the torus, the stratospheric composition, and the aurora. On the ESA-SERC side, two PIs were allocated time. Renee Prange was allocated 21 shifts to study the aurora and stratosphere and Michel Festou was allocated 4 shifts to study the torus. The NASA and ESA-SERC teams will attempt to coordinate their observations, leading to essentially continuous coverage during the impact week.
The above includes excerpts from Glenn Orton's IJW newsletters,
Willem Wamsteker's article in ESA's AstroNews and additional information
from Tim Livengood.