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| imagerteleconnotes20180124 [2018/01/24 13:16] – hanany | imagerteleconnotes20180124 [2018/02/01 11:29] (current) – bcrill | ||
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| * Attitude control requirements | * Attitude control requirements | ||
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| + | | | (arcsec) | ||
| + | | EPIC | <35 (3 sigma) | ||
| + | | CORE | 1 (1 sigma) | ||
| + | | PICO | 6 (1 sigma) | ||
| === Notes:=== | === Notes:=== | ||
| + | |||
| + | Notes: | ||
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| + | Attitude control | ||
| + | * Shaul: Pointing Control is how well spacecraft points at a direction; Pointing Knowledge is how well we know where it points at; Pointing stability is how stable pointing is in terms of changing rate. | ||
| + | * Ben: thinking about map to understand definitions of pointing knowledge, control and stability; that's how engineers talk about them. | ||
| + | * PICO rquires 6 arcsec pointing knowledge, which about 1/10 of the smallest beam. | ||
| + | * Shaul thinks we do not need more than 1 degree of pointing control. | ||
| + | * Bill: pointing stability is associated with spin; we may also think about how stable spin axis is aligned with star camera. | ||
| + | * Bill: points out having 2 or more scan modes would have been very helpful for Planck. Break time constant and beam shape degeneracies. Shaul: right now we fix on having only 1 scan strategy, but it can be discussed. | ||
| + | * Jacques: 3 star sensors garuntees 1'' | ||
| + | * Jacques: Thoughts from CORE, | ||
| + | * Pointing control is to eliminate gaps in map. 24'' | ||
| + | * 24'' | ||
| + | * Shaul: reaction wheels are current assumption for PICO | ||
| + | * **A/I** Shaul to check with Amy about 24'' | ||
| + | |||
| + | * Additional note from Brendan: Planck achieved 2 arcsecond rms pointing reconstruction [[https:// | ||
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| + | I + T, lessons from Planck, options for PICO. (Tomo) | ||
| + | * Plank tested mirrors + baffles, then focal plane and feeds separately | ||
| + | * example of parameters that need to be tested in presentation page 5 | ||
| + | * tests at component and subsystem levels. | ||
| + | * feed beam patterns not tested cold | ||
| + | * Jacques: Primary, secondary at different temperatures. difficult to test this on ground. Alignment may create issues. | ||
| + | * Planck cold system test at CSR. Signal response test, but no beam mapping. | ||
| + | * Photogrammetry of full structure to measure alignment, and align system. | ||
| + | * 10 um interferometry of planck mirrors. | ||
| + | * optics needed to be sufficiently polished for this test. may need to ' | ||
| + | * also consider mirror material in cost, planck was CFRP. | ||
| + | * focal plane testing at Saturne. criteria tested on page 13. | ||
| + | * Comments for PICO: | ||
| + | * page 16-17, cost drivers. 3 cyrostats (all large), plus full satellite sized chamber to test full system (cooling, etc.) | ||
| + | * cold testing drives cost, dependent on availible facilities, dependent on what is characterized in flight vs on ground | ||
| + | * page 19, calibrations done for Planck shown. | ||
| + | * spectral response not fully measured on ground, can't be sense | ||
| + | * Shaul: has Planck over tested or under tested any optics? | ||
| + | * Bill: most valuable was cold photogrammetry of flight optics. Other tests were of interest, but not as critical. | ||
| + | * Mirror material? | ||
| + | * Shaul: TeamX assumed aluminum mirrors. Silicon carbide may over run cost. Aluminum below $10M. | ||
| + | * Discussion on hold until next week due to time. | ||
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