VI. Analysis of Release Products

1. Comparison of Achieved Performance with Level 1 Science Requirements

Table 1 - Preliminary Release Achieved Performance
 Level 1 RequirementAchieved
Sky Coverage
≥4 independent exposures in each filter on at least 95% of the sky≥4 coverages on >99% of the sky, all bands.
95% of sky has 10.0/9.9/9.0/9.4 coverages in W1/W2/W3/W4
(Preliminary Data Release covers 57% of the sky)
Photometric Sensitivity
SNR=5 at 0.12/0.16/0.85/4.0 mJy (16.0/15.1/11.3/8.3 Vega mag) at W1/W2/W3/W4 in unconfused regions with 8 coverages0.05/0.10/0.73/5.9 mJy (17.0/15.6/11.5/7.9 Vega mag) based on comparison with external measurements
Photometric Accuracy
RMS error in relative accuracy <7% accuracy for SNR>100 RMS = 0.02 mag (W1/W2/W3) and 0.03 mag (W4)
Astrometric Accuracy
RMS position error with respect to the 2MASS PSC <0.5" for SNR>20 in at least one bandRA and Dec RMS~0.2" for W1<13.0 mag. Increasing fraction of fainter sources exhibit a systematic declination bias of 0.2-1.0". Approx. 20% of sources with W1<14.5 mag are affected.
Catalog Completeness
>95% for SNR>20 in unconfused regions> 95% for sources with W1<16.6, W2<16.0, W3<10.8, W4<6.7 Vega mag in unconfused regions with ≥12 frame depth-of-coverage
Catalog Reliability
>99.9% for SNR>20 in unconfused regions> 99.9% for sources with W1<15.6, W2<14.3, W3<10.2, W4<6.5 mag in unconfused regions with ≥12 frame depth-of-coverage.

Last update: 2011 April 13

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