The Cobra fiber positioner is being developed by the California Institute of Technology (CIT) and the Jet Propulsion
Laboratory (JPL) for the Prime Focus Spectrograph (PFS) instrument that will be installed at the Subaru Telescope on
Mauna Kea, Hawaii. PFS is a fiber fed multi-object spectrometer that uses an array of Cobra fiber positioners to rapidly
reconfigure 2394 optical fibers at the prime focus of the Subaru Telescope that are capable of positioning a fiber to
within 5μm of a specified target location. A single Cobra fiber positioner measures 7.7mm in diameter and is 115mm
tall. The Cobra fiber positioner uses two piezo-electric rotary motors to move a fiber optic anywhere in a 9.5mm
diameter patrol area. In preparation for full-scale production of 2550 Cobra positioners an Engineering Model (EM)
version was developed, built and tested to validate the design, reduce manufacturing costs, and improve system
reliability. The EM leveraged the previously developed prototype versions of the Cobra fiber positioner. The
requirements, design, assembly techniques, development testing, design qualification and performance evaluation of EM
Cobra fiber positioners are described here. Also discussed is the use of the EM build and test campaign to validate the
plans for full-scale production of 2550 Cobra fiber positioners scheduled to begin in late-2014.
A graphical user interface (GUI) for bandmerging is presented. The purpose of the Bandmerge GUI is to provide an integrated graphical user interface for running the bandmerge module and its support modules to provide astronomers with an interactive tool for bandmerging. The bandmerge module identifies multi-band detections of an individual point source and merges the information in the different bands into a single record of the source. The developed Java Application provides an interface to downlink software, which is normally invoked on the command line. With the Bandmerge GUI, a SPITZER general user can select the data to be processed, specify processing parameters, and invoke the Bandmerge pipelines.
Commercial applications for fiber sensing and low-coherence interferometry are rapidly growing in medical, industrial and aerospace markets. These new instruments must be smaller, more robust and less expensive. An all-fiber optical delay line or “fiber stretcher”, using piezoelectric (PZT) actuation, offers a simple solid-state solution that eliminates free space optics. The challenges for PZT fiber stretchers include: reducing non-linearity and hysteresis, achieving sufficient scan range with minimum fiber length, maximizing scan frequency and reducing losses in the drive electronics. PZT actuators are essentially large ceramic capacitors that must be rapidly charged and discharged to achieve fast scanning. The mechanical response of the PZT ceramic is greater than 10 kHz which makes it practical to scan at four kilohertz. A thin-walled piezoelectric disk or cylinder achieves 4.5 millimeters of fiber stretch using 20 meters of coiled fiber. Digitally controlled series resonant electronics produce a 1200 volt sinusoidal drive signal at a fixed frequency of four kilohertz while dissipating only 16 Watts. An all-fiber optical delay line module, using piezoelectric actuators and a series resonant drive, is a miniature, robust and efficient alternative to free-space optics with dithering mirrors or spinning polygons.
The Multiband Imaging Photometer for Spitzer (MIPS) provides long wavelength capability for the mission, in imaging bands at 24, 70, and 160 microns and measurements of spectral energy distributions between 52 and 100 microns at a spectral resolution of about 7%. By using true detector arrays in each band, it provides both critical sampling of the Spitzer point spread function and relatively large imaging fields of view, allowing for substantial advances in sensitivity, angular resolution, and efficiency of areal coverage compared with previous space far-infrared capabilities. The Si:As BIB 24 micron array has excellent photometric properties, and measurements with rms relative errors of 1% or better can be obtained. The two longer wavelength arrays use Ge:Ga detectors with poor photometric stability. However, the use of 1.) a scan mirror to modulate the signals rapidly on these arrays, 2.) a system of on-board stimulators used for a relative calibration approximately every two minutes, and 3.) specialized reduction software result in good photometry with these arrays also, with rms relative errors of less than 10%.
To keep pace with the increasing demand for higher throughput, lower cost per unit and tighter specifications, manufacturers of fiber optic devices are now looking towards a new generation of automated alignment tools. The ideal alignment tool has six degrees-of-freedom (DOF), (X,Y,Z, Yaw, Pitch, Roll) repeatability better than 50 nanometers, travel greater than 10 millimeters and is fully automated. In this paper we describe the use of INCHWORM motor technology to produce a new nano-robotic system that demonstrates a major advancement toward the ideal photonics alignment tool. The INCHWORM actuator is uniquely suited to provide nanometer resolution movements over tens of millimeters of range with very high stiffness and stability. The clamp-extend-clamp-retract stepping sequence produces direct linear motion with no backlash. INCHWORM motors are integrated in cross roller bearing stages to achieve 20 nanometer and 0.1 arc second closed-loop resolution. The high stiffness and stability of the solid-state piezoelectric actuators hold position to a single count on a glass scale encoder while generating zero heat. Mounting fixtures hold optical elements so that their geometric centers coincide with the virtual point of rotation. Active alignment processes for selected photonics components, as well as intensity maps of components are presented.
A new NGST InchwormR motor design is described that meets the demanding actuator requirements of the Next Generation Space Telescope. The classic Inchworm motor does not function at cryogenic temperatures. The interference fit between the motor and shaft gets tighter and breaks the clamps and 80 percent of piezoelectric (PZT) movement is lost at 20 degrees K. The NGST Inchworm concept maintains a constant fit over a wide temperature range and the loss of PZT motion is compensated for by adding extra PZT material or potentially by incorporating new cryogenic active materials that are currently being developed by other companies. Another significant improvement of the NGST Inchworm is the ability to hold position when power is removed (i.e. zero charge on all actuators) with zero PZT creep. This makes it possible for the NGST Inchworm and electronics to dissipate zero power when holding position for days or weeks. The NGST Inchworm will have a new clamp design that has at least ten times lower clamp 'glitch' than the classic Inchworm. Low clamp glitch makes it possible to move to a desired position with nanometer resolution and deactivated the motor without disturbing the output position more than a few nanometers.
This document discusses material selection, design, and analysis of a composite gimbal for use on a high precision inertial guidance test table with active magnetic bearing suspension. The test table's system performance goals of 0.1 arc second angular pointing accury and one part per million angular rate stability, can only be achieved by using a gimbal with high specific stiffness, highly symmetric elastic properties, and high dimensional stability. These characteristics are achieved by proper selection of the ginthal's construction material, configuration, and fabrication processes. Both traditional and advanced composite materials are considered and evaluated for specific stiffness, coefficient of thermal expansion, thermal conductivity, dimensional stability, fabrication problems, and cost. Using the candidate materials, several gimbal configurations are evaluated with respect to the test table's system performance goals for angular pointing accuracy and angular rate stability. Specific gimbal design parameters affecting the system performance goals for angular pointing accuracy and angular rate stability include: the angular payload deflections due to torsional wind-up and asymmetrical stiffness; the linear payload deflections that cause torque disturbances and shaft wobble; and the natural frequencies affecting the control system bandwidths. Detailed finite element models of each configuration are used to predict the performance charteristics and demonstrate the advantages of the graphite/epoxy composite design.