| IOC-MIPS_245a | 10470C | ||||||||
| Title: | Optimum Bias Setting for MIPS Detectors | ||||||||
| Objective: | Determine the best detector bias for each MIPS array | ||||||||
| Description: | Three performance criteria, (responsivity, dark current, latent images) will be checked as a function of bias. | ||||||||
| including flow / state diagram | A total of five bias settings will be tested. The same setting as used in thermal-vac will be used here. | ||||||||
| Part 1: | Bias test on the 24um array, dark current, responsivity, and latent images must be checked. | ||||||||
| At each of five bias voltages: | |||||||||
| Dark current/read noise: | Take 25 30-second exposures with the scan mirror in the dark position. | ||||||||
| Responsivity/latent images: | Use the 10-second exposure mode and a 4x4 dither pattern while | ||||||||
| observing a moderately bright star. | |||||||||
| Part 2: | Bias test on the 70um array, dark current and responsivity need to be checked. | ||||||||
| At the beginning of the test, perform a thermal anneal. | |||||||||
| At each of five bias voltages: | |||||||||
| Dark current/read noise: | Take 25 10-second exposures with the scan mirror in the dark position. | ||||||||
| Responsivity: | Use the 10-second exposure mode and a 4x4 dither pattern while | ||||||||
| observing a moderately bright star. | |||||||||
| Part 3: | Bias test on the 160um array, dark current and responsivity need to be checked. | ||||||||
| At the beginning of the test, perform a thermal anneal. | |||||||||
| At each of five bias voltages: | |||||||||
| Dark current/read noise: | Take 25 10-second exposures with the scan mirror in the dark position. | ||||||||
| Responsivity: | Use the 10-second exposure mode and the photometry mode, | ||||||||
| observing a moderately bright star at 6 positions on the array. | |||||||||
| Place in Schedule: | |||||||||
| (relative to water shed events) | |||||||||
| Required Conditions: | Telescope must be at its final operating temperature of 5.5K. | ||||||||
| MIPS apertures must already have been located and all detector and electronics . | |||||||||
| checkouts must have been performed. | |||||||||
| Resources: | |||||||||
| duration (best estimate) | 3 hrs | ||||||||
| real time downlink (Y / N) | No | ||||||||
| special post event actions (Y / N) | No | ||||||||
| Dark current test generates 3x25x5 = 375 DCEs. | |||||||||
| Responsivity test generates 5x(16+16+6) = 190 DCEs | |||||||||
| Outcome: | |||||||||
| description | The optimum bias setting for each array will be known. | ||||||||
| can proceed in parallel with other activity | No, requires dedicated pointing. | ||||||||
| must outcome be confirmed before next event / test /activity | Yes, selection of biases must be made before read noise / dark current test. | ||||||||
| method of confirmation (sensor TLM, data analysis, etc.) | Data analysis. | ||||||||
| estimate of data turn around if required for confirmation | 48 hrs. | ||||||||
| Unique or included in planned AOT? | |||||||||
| Changing biases is an engineering command but data acquisition can use dark current IET | |||||||||
| and photometry AOT. | |||||||||
| Contingency Plan: | |||||||||
| "What if..." | Worst outcome would be that changing bias made no difference. If test failed to execute, | ||||||||
| the thermal-vac test bias results could be used. | |||||||||
| IOC Critical | Y | ||||||||
| References: | |||||||||
| Template last updated: | 9/6/99 | ||||||||
| M. Rieke | |||||||||