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Mission Planning Updates

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Presentation on theme: "Mission Planning Updates"— Presentation transcript:

1 Mission Planning Updates
Chandra User’s Committee Meeting (09/29/15) P. Slane (Chandra Mission Planning)

2 Thermal Balance: A Reminder
Maximum Dwell for Sample S/C Component Brown: maximum exposure before exceeding temperature limit Blue: minimum cooling time required to return to state from which another max dwell possible Note that this is only for one of the multiple spacecraft components with temperature limits Complete Science Orbit RadZone ObsID Temperature Prediction (degF) Scheduling is a balance of heating and cooling multiple s/c components - Observations often split to accommodate temperature limits 2 Chandra User’s Committee Meeting (09/29/15) P. Slane (Chandra Mission Planning)

3 ACA Constraints on Mission Planning
Chandra uses Aspect Camera to determine attitude, maintain pointing, and provide post-facto image reconstruction data Typically, 8 acquisition stars are used to acquire target attitude. - practical minimum brightness is M ≈ 10.6 For guide and aspect reconstruction, typical configuration is 5 guide stars and 3 fiducial lights Chandra User’s Committee Meeting (09/29/15) P. Slane (Chandra Mission Planning)

4 ACA Constraints on Mission Planning
Increasing temperatures for aspect camera result in increase in hot/warm pixels - Effective background increases, making it more difficult to detect faint stars - Planning constraints needed to limit camera temperature; TACA < -14C Result is a limitation on continuous dwell time at particular spacecraft orientations - In addition, post-observation cooling attitudes required before returning to such “hot” orientations. Chandra User’s Committee Meeting (09/29/15) P. Slane (Chandra Mission Planning)

5 ACA Constraints on Mission Planning
Increasing temperatures for aspect camera result in increase in hot/warm pixels - Effective background increases, making it more difficult to detect faint stars - Planning constraints needed to limit camera temperature; TACA < -14C Result is a limitation on continuous dwell time at particular spacecraft orientations - In addition, post-observation cooling attitudes required before returning to such “hot” orientations. Chandra User’s Committee Meeting (09/29/15) P. Slane (Chandra Mission Planning)

6 ACA Constraints on Mission Planning
Increasing temperatures for aspect camera result in increase in hot/warm pixels - Effective background increases, making it more difficult to detect faint stars - Planning constraints needed to limit camera temperature Result is a limitation on continuous dwell time at particular spacecraft orientations - In addition, post-observation cooling attitudes required before returning to such “hot” orientations. Chandra User’s Committee Meeting (09/29/15) P. Slane (Chandra Mission Planning)

7 ACA Constraints on Mission Planning
For given target, star field is investigated for each day of year to determine how warm camera can be (Tobs,max) while still ensuring sufficient detectable stars. - Both nominal (red) and off-nominal (blue) roll angles are considered. If Tobs,max is above the planning limit (-14C), then we are assured of getting stars as long as the observation can be scheduled at all. Time intervals with Tobs,max > -14C are identified as window constraints for placement of observations. ObsID 18201 Sunblock Planning Limit ( window ( ) ( ) X18201 ) ( window ( ) ( ) X18201 ) ( window ( ) ( ) X18201 ) ( window ( ) ( ) X18201 ) ( window ( ) ( ) X18201 ) ( window ( ) ( ) X18201 ) Chandra User’s Committee Meeting (09/29/15) P. Slane (Chandra Mission Planning)

8 MLI: Long-Term Trends Chandra Spacecraft
+Y Chandra Spacecraft -Z +X Thermal effects result from the slow degradation of thermal multilayer insulation (MLI). Initial trends suggested eventual flatting of temperature increase. With more data, trend appears linear. - Current data indicate linear increase for remainder of mission. Chandra User’s Committee Meeting (09/29/15) P. Slane (Chandra Mission Planning)


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