ASTRO-F > Operation Plan

Operation Plan

Orbit and Attitude Control Mode

The orbit of ASTRO-F is a Sun synchronous polar orbit with an altitude of 745 km. It goes around the Earth above the twilight zone and passes over the North and South Poles. The orbital period is approximately 100 minutes.

Observations with ASTRO-F are performed in two attitude control modes; the survey mode and the pointing mode.

Survey Mode

Survey Mode

Survey mode is the basic observation mode of ASTRO-F. The attitude of the satellite is always set so that the direction of the telescope is perpendicular to the directions of the Sun and the Earth. Therefore the telescope spins and scans the sky along a great circle as the satellite goes around the Earth. The direction of the Sun from the Earth rotates once in a year. Consequently, ASTRO-F can make an all-sky survey in half a year in the survey mode.


 

Pointing Mode

Pointing Mode

Pointing mode is used in the case when an observer requests a long exposure or spectroscopy toward a fixed location. The telescope cannot point in an arbitrary direction at any time, because the telescope cannot look in the direction from which the light of the Sun and/or the Earth come. Due to this restriction, any exposure time is less than ten minutes for one observation.


 

Observation Period

The operational life of ASTRO-F ends when the liquid Helium, the principal coolant onboard ASTRO-F, runs out. The expected lifetime is estimated to be about 550 days after launch.

The operation plan is as follows. The first two months of the mission is the performance verification (PV) phase. In the following a half year, the FIS all-sky survey is preferentially performed (Phase 1). After Phase 1, ASTRO-F observes various objects in the pointing mode in addition to complementing the missed areas from Phase 1, until the liquid Helium is consumed. The near-infrared camera of the IRC can continue observations after the Helium expires, because the near-infrared camera can be used at the temperature kept by the mechanical coolers only.

There will be gaps in the surveyed areas due to the Moon and so on. These gaps are filled after a half year.

Pointing observations are made three times per an orbital revolution at maximum.

ASTRO-F is equipped with mechanical coolers in addition to liquid Helium. Consumption of the Helium is suppressed by using mechanical coolers.

←PREV | INDEX↑ | NEXT→
ASTRO-F > Operation Plan