NASA Uses NI LabVIEW to Save Time, Reduce Costs in Automated Testing of Microshutters

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"This new technology promises datasets unimaginable with today’s sensors but requires proven lifetime longevity."

- David McAndrew, Mink Hollow Systems

The Challenge:
Developing a flexible test application that can actuate tens of thousands of micron-sized shutter elements (microshutters) for millions of cycles while logging data, acquiring high-resolution images, and monitoring and controlling the test environment.

The Solution:
Using a National Instruments application based on LabVIEW so the user can configure and run custom shutter actuation tests while monitoring and controlling the test environment.

David McAndrew - Mink Hollow Systems
David Mostofi - Sigma Space
David Rapchun - Global Science and Technology/NASA-Goddard Space Flight Center

Role of Microshutter Arrays for the James Webb Space Telescope

As the Hubble Space Telescope nears its twilight, our appetite for space exploration has only intensified. The James Webb Space Telescope (JWST) is our next stepping-stone toward understanding the universe and studying the Big Bang theory. With these lofty goals come intense challenges: development of new, lightweight materials for larger apertures; improved detector technology for faint signals; and microshutter arrays for sensing hundreds of simultaneous spectra. Using LabVIEW to test microshutter arrays, we can detect and diagnose problems early in development and greatly reduce overall cost.

The need for microshutters in the near infrared spectrometer (NIRSpec) came from the following mission constraints:

  • A single spectral measurement can take days, making the need for a multisensing device critical.
  • Without an aperture mask, spectral overlap contaminates data sets resulting in unusable data.
  • The mask must be configurable to change with the motion of the satellite.

From these constraints, NASA Goddard Space Flight Center developed programmable aperture masks (microshutters) to meet the JWST mission goals.

Operation of a Microshutter Array

A microshutter array consists of tens of thousands of 100um x 200um shutter elements that can be individually held open or closed to create a custom image mask based on the sensor field of view. In operation, elements are opened where objects exist and closed where interference between objects would occur on the detector.

Sweeping a magnet across the array pulls the shutters open. By applying a voltage to the appropriate row and column of the array, an individual shutter can be held open after the magnet passes. Non-powered shutters will close.

Incorporating Tester Hardware

The goals of the microshutter tester are twofold: 1) provide design feedback and 2) estimate unit life. Because the testing environment must mimic the conditions of space, the software delivers system monitoring and control of temperature and pressure using GPIB instrumentation. With this control, users can subject units to various temperature profiles that simulate the effects of solar warming.

To provide design feedback and estimate unit life, the automated tester actuates shutter elements repeatedly while capturing images at specific intervals. A GPIB power supply and digitally driven relays supply power to the arrays. NI PCI-7344 controllers and NI MID-7604 drivers control magnet motion and three-axis camera positioning for images taken during testing. If the user finds a problem, they can put the system into a higher-resolution “image-mosaic” mode that scans a camera with 4-micron resolution, yielding more detailed data of individual shutters. Users stitch together individual images are using NI Silver Alliance Partner Mink Hollow Systems MosaicVIEW software.

Progressing Technology through Flexible Test

We created modular test software to configure custom tests and add or change instruments with minimal code changes. Duplicate test fixtures in the controlled environment required the software to simultaneously run two tests. Incorporating many different instruments and maintaining modular code made LabVIEW an obvious choice for our development language.

A test procedure is a list of commands sent to the tester where each command is a predefined function. With the use of procedures, users can configure new tests without code changes.

For example, a test procedure to cycle an array with imaging may be created as:

  • Power microshutter elements
  • Sweep magnet across array (all shutters open)
  • Capture image
  • Remove power from microshutter array (all shutters close)
  • Capture image

Users can compare this test to a test where the magnet is swept across the array before the last image is captured. The results yield insight into the spring force on the elements if they intermittently stay closed without an additional magnet sweep.

Test cycles with imaging require significantly more time than a cycle without imaging. To perform a test that cycles millions of times but still acquires images, we designed the system to allow two test procedures. These two cycling procedures combine in a test script that lists the number of magnet cycles to complete before running the imaging procedure. With this capability, the user can create tests that take more images at the beginning of a test and fewer as the test progresses, providing both increased test speed and image feedback. This is a vital feature because early testing of microshutters revealed that shutter failure probability decreases as the number of actuations increases.

To accommodate changes to the test station, instrument drivers are implemented as objects for easy device-type addition. For example, in the next-generation tester, a QImaging camera is replaced with a Sony. Despite differences in drivers, the software includes an imaging object where the methods and properties remain the same but the underlying code is product specific. With this design, we achieve seamless integration of the new camera while maintaining a single version of the overall software and, most importantly, we eliminate the need for updating test procedures.

Saving Time, Reducing Costs

The NIRSpec with microshutter arrays gives scientists the capability of simultaneously acquiring hundreds of spectra from the James Webb Space Telescope – a first in space-based astronomy. This new technology promises datasets unimaginable with today’s sensors but requires proven lifetime longevity. Our automated tester helps study the performance and verify the feasibility of the microshutters by giving users the freedom to perform custom tests and rapidly adapt to new test instrumentation and with minimal effort. Using LabVIEW, we completed the modular test software quickly, which gave us time to detect and diagnose problems early in development, greatly reducing overall costs.

For more information, contact:

David McAndrew

Test Engineer

Mink Hollow Systems

6880 Mink Hollow Rd.

Highland, MD 20777

Tel: (301) 854-1579

Fax: (301) 854-9756


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