Evaluation of Digital Micromirror Devices for use in space-based Multi-Object Spectrometer application

摘要

The astronomical community continues to be interested in suitableprogrammable slit masks for use in multi-object spectrometers (MOSs) on spacemissions. There have been ground-based MOS utilizing digital micromirrordevices (DMDs) and they have proven to be highly accurate and reliableinstruments. This paper summarizes the results of a continuing study toinvestigate the performance of DMDs under conditions associated with spacedeployment. This includes the response of DMDs to radiation, to the vibrationand mechanical shock loads associated with launch, and the operability of DMDunder cryogenic temperatures. The optical contrast ratio and a study of thelong-term reflectance of a bare device have also been investigated. The resultsof the radiation testing demonstrate that DMDs in orbit would experiencenegligible heavy-ion induced single event upset (SEU) rate burden, we predictSEU rate of 5.6 micromirrors per 24 hours. Vibration and mechanical shocktesting was performed according to the NASA General Environmental VerificationStandard (GEVS), no mirrors failed in the devices tested. The results of lowtemperature testing suggest that DMDs are not affected by the thermal load andoperate smoothly at temperatures at least as low as 78 K. The reflectivity of abare DMD did not measurably change even after being exposed to ambientconditions over a period of 13 months. The measured contrast ratio (on state vsoff state of the DMD micromirrors) was greater than 6000/:1 when illuminatedwith an f/4 optical beam. Overall, DMDs are extremely robust and promise toprovide a reliable alternative to micro shutter arrays (MSA) to be used inspace as remotely programmable slit masks for MOS design.