Table 2
Simulation results for stars with 95% diluted five year observation histories, where the spacecraft attitude was determined by a separate solution from well-observed stars.
| Prior σϖ,p | Fraction in 90% conf. ellipse | Actual position errors [mas] | ||||
| G ≃ 11 | G ≃ 15 | G ≃ 19 | G ≃ 11 | G ≃ 15 | G ≃ 19 | |
|
|
||||||
| Subset of stars with ≤4 field-of-view transits | ||||||
|
|
||||||
| none (2 parameters) | 0.5% | 1.8% | 13.5% | 33.0 | 16.3 | 15.2 |
| 0.01 mas | 1.5% | 3.5% | 14.3% | 21.8 | 12.1 | 14.8 |
| σϖ,F90 | 90.1% | 91.4% | 91.2% | 7.6 | 4.3 | 7.6 |
| 10σϖ,F90 | 92.7% | 93.3% | 94.4% | 8.4 | 5.2 | 10.5 |
| 1000 mas | 92.5% | 93.0% | 93.3% | 8.6 | 7.4 | 15.5 |
|
|
||||||
| Subset of stars with >4 field-of-view transits | ||||||
|
|
||||||
| none (2 parameters) | 0.3% | 0.8% | 8.6% | 21.0 | 11.3 | 9.7 |
| 0.01 mas | 3.1% | 5.4% | 10.4% | 6.7 | 5.0 | 8.9 |
| σ ϖ,F90 | 89.4% | 89.9% | 90.3% | 0.2 | 0.3 | 1.6 |
| 10σϖ,F90 | 89.5% | 89.8% | 90.5% | 0.2 | 0.3 | 2.0 |
| 1000 mas | 89.5% | 89.8% | 90.0% | 0.2 | 0.3 | 2.2 |
Notes. A prior uncertainty ≥σϖ,F90 provides a sensible solution for all stars. Column 1: prior uncertainty used in the solution. Columns 2–4: fractions of actual position errors contained in the 90% confidence ellipses calculated from the formal covariances; ideally, these values should be around 90%. Columns 5–7: 90th percentile values of the actual position errors (estimated minus true value) in mas; these should be as small as possible. For comparison: two parameter solution (position only) without a prior.
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