SCUBA noise migrates across arrays

03 July 2000
During June the noise on the LW array was increasing in a matter of only a couple of days following miniwarmups. Repeated miniwarmups hold dangers for the instrument inasmuch as internal components may survive only a limited number of such thermal cycles.

An extended mini-warmup (excuse the lack of a better term) was imposed during the scheduled SMU repair June 21-28 incl., but the noise on the LW array returned soon after. The noise migrated across the array over the weekend of July 01 and it seemed likely that more drastic action would be needed. However, the noise continued to migrate and cleared off the LW array on July 03 (UT), appearing on and migrating across the SW array instead.

Optimistically, the noise, and the causative agent, will migrate off the SW array also in a few days.

12 July 2000
We were unable to watch this migration reach its ultimate conclusion, as a cryogenic blockage occurred on July 04 requiring another warmup. SCUBA cooldown completed successfully on July 11 - we're waiting now to see the noise performance over the next couple of days.

28 Sep 2000
Noise performance since has been very good; the SW array has been particularly quiet, while there are only ever the same small number (3 or 4) of pixels (g13,i2,i9 and an occasional other) on the LW array that deviate from the normal low mean values :