The Pan-STARRS telescopes are a distributed aperture approach to rapid, multi-color wide-field surveys. The first of these telescopes, a prototype designated PS1, has been in operation now for over three years and has already obtained complete sky coverage of the full 3-π steradians visible from Haleakala in 5 broad passband filters at multiple epochs. On average the PS1 survey has obtained approximately 12 epochs though each filter. The second telescope, designated PS2, has been in its commissioning phase since August 2013 and will begin science operations in the second half of 2014. Several design and fabrication changes in both the telescope and the camera have been implemented in PS2. This talk will describe the science results that have been coming out of the PS1 survey, the design changes implemented on PS2, and the current performance of the PS2 telescope and camera. We will also describe the future missions for the PS1 and PS2 telescopes as of the current year.
The PS2 telescope is the second in an array of wide-field telescopes that is being built for the Panoramic-Survey
Telescope and Rapid Response System (Pan-STARRS) on Haleakala. The PS2 design has evolved incrementally based
on lessons learned from PS1, but these changes should result in significant improvements in image quality, tracking
performance in windy conditions, and reductions in scattered light. The optics for this telescope are finished save for
their coatings and the fabrication for the telescope structure itself is well on the way towards completion and installation
on-site late this year (2012). The most significant differences between the two telescopes include the following:
secondary mirror support changes, improvements in the optical polishing, changes in the optical coatings to improve
throughput and decrease ghosting, removal of heat sources inside the mirror cell, expansion of the primary mirror figure
control system, changes in the baffle designs, and an improved cable wrap design. This paper gives a description of each
of these design changes and discusses the motivations for making them.
The Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) is an innovative design for a wide-field imaging facility developed at the University of Hawaii's Institute for Astronomy. The Pan-STARRS prototype telescope (PS1) is an Altitude over Azimuth telescope with an instrument rotator for its 1.4gigapixel camera.
Quartus Engineering Incorporated (Quartus) performed modal survey and operational vibration testing of the Pan-STARRS prototype telescope (PS1) to assess the impact of structural resonance and star tracking (i.e. actuated telescope motion) on image quality. The telescope's modal parameters: resonant frequencies, modes shapes, and damping ratios; were measured using an impact hammer and the acceleration response gathered from components with natural modes of vibration identified in a pre-test structural analysis that that were thought to affect image quality. A baseline characterization of the PS1's elastic performance was performed and compared with real-time structural modifications to determine how an individual component's stiffness affects the telescope's overall elastic performance. Operational vibration data collected at various on-sky tracking states was then evaluated using the newly measured modal properties and legacy optical measurements to develop a relationship between elastic motion and image quality.
Pan-STARRS is a highly cost-effective, modular and scalable approach to wide-field optical/NIR imaging. It uses 1.8m
telescopes with very large (7 square degree) field of view and revolutionary1.4 billion pixel CCD cameras with low
noise and rapid read-out to provide broad-band imaging from 400-1000nm wavelength. The first single telescope system,
PS1, has been deployed on Haleakala on Maui, and has been collecting science quality survey data for approximately six
months. PS1 will be joined by a second telescope PS2 in approximately 18 months. A four aperture system is planned to
become operational following the end of the PS1 mission. This will be able to scan the entire visible sky to
approximately 24th magnitude in less than a week, thereby meeting the goals set out by the NAS 2000 decadal review for
a "Large Synoptic Sky Telescope". Here we review the technical design, and give an update on the progress that has
been made with the PS1 system.
The PS1 is a wide-field survey telescope which is a prototype for the Pan-STARRS project. It has a 7 square degree
field of view, a 1.85-m primary mirror, a 0.9-m secondary mirror, 6 interference filters with 0.48-m diameters, and
three corrector lenses with diameters between 0.6 and 0.4-m. The PS1 camera (GPC1) has 0.26" square pixels in a
format that includes 1.44 Giga-pixels. The PS1 camera is located on the summit of Haleakala on the island of Maui
which has a median seeing of 0.8-0.9". The PS1 telescope has been under commissioning since September 2007. This
article describes the mounting and the supports of the PS1 optics as well as the efforts that have been made towards
achieving site-limited image quality in the alignment of the telescope optics. We also show here some of the early
imaging from this telescope as a function of time during commissioning.
The Pan-STARRS project is planning to build a suite of four telescopes (PS4) on the summit of Mauna Kea at the site of
the current University of Hawaii 2.2-m telescope. These telescopes will have the goal of surveying the entire sky visible
from a single site in 5 colors (g, r, i, z, and y) on the time scale of approximately 1 week at a spatial resolution limited
primarily by the quality of the site. To accomplish this task each of these four telescopes will be equipped with a
Giga-Pixel camera, a camera shutter, and a 6 filter mechanism. A prototype telescope for this project (PS1) that includes all of
these subsystems is already under going commissioning. The project is currently involved in developing the
Environmental Impact Statement that is required to build the PS4 array of telescopes. We give an overview here of the
scientific goals, the instrumentation package, the telescope design, and the enclosure design for the PS4 system.
Pan-STARRS, the Panoramic Survey Telescope and Rapid Response System, is a project to first develop a single wide field synoptic survey telescope (Pan-STARRS-1) followed by a system of four such telescopes. It is designed to accomplish many of the science goals envisioned by the decadal review for LSST. The primary mission of Pan-STARRS is the detection of potentially hazardous asteroids (PHA), secondary science objectives are a (nearly) all-sky survey, a medium-deep survey, an ultra-deep survey, and studies of transients and variable objects. This paper presents the current status of the telescope design, with emphasis on the optics.
A stray light analysis of the Apache Point Observatory 3.5 meter telescope system was done to understand the performance for a variety of imaging modes. The telescope system consists of the 3.5-m telescope, its enclosure, and its associated imaging cameras. The purpose of the study was to assess the stray light performance of this system, identify where modification(s) would improve the system off-axis rejection characteristics, and assess the effectiveness of those modifications. A detailed telescope system geometry model was created, and scatter models were created for telescope and enclosure components. The computer model we created duplicated the pinhole stray light images taken with the telescope, thereby verifying the model. The Point Source Transmittance (PST), a commonly used metric for assessing stray light was used to evaluate the stray light performance of the system for a number of off-axis angles and to suggest modifications to enhance the system. The baseline PST of the existing system shows virtually no falloff with off-axis angle in the plane of the observatory slit. This is the result of (1) the focal plane having a large, unobstructed view of the Nasmyth mirror and cell, primary mirror cell, and baffles mounted on the Nasmyth cell, (2) relatively unobstructed illumination of telescope over a large range of angles in the plane of the slit, and (3) secondary and Nasmyth baffles that are not enclosed. These attributes create a series of first-level scatter paths that directly illuminate the focal plane. Our approach to stray light reduction was to address the light paths revealed by the various PST calculations. Our calculations have shown that significant gains can be realized with simple modifications to the telescope system.
The HiRES High-Resolution EUV Spectroheliometer is a sounding rocket instrument yielding very high spatial, spectral, and temporal resolution images of the solar outer atmosphere, on the basis of a 45-cm Gregorian telescope feeding a normal-incidence stigmatic EUV spectrometer with imaging multianode microchannel-array detector system, as well as an IR spectrometer with imaging CCD detector system. Attention is given to the expected performance of this system, including the effects of vibrational misalignments due to the sounding rocket flight environment.
The Multi-Anode Microchannel Array (MAMA) is a photon counting detector which utilizes a photocathode for photon to electron conversion, a microchannel plate (MCP) for signal amplification and a proximity focused anode array for position sensitivity. The detector electronics decode the position of an event through coincidence discrimination. The decoding algorithm which associates a given event with the appropriate pixel is determined by the geometry of the array. A new algorithm incorporated into a CMOS Application Specific Integrated Circuit (ASIC) decoder which improves the pixel spatial resolution is described. The new algorithm does not degrade the detector throughput and does not require any modifications to the detector tube. The standard MAMA detector has a pixel size of 25 x 25 square microns, but with the new decoder circuit the pixel size is reduced to 12.5 x 12.5 square microns. We have built the first set of decode electronics utilizing the new ASIC chips and report here on the first imaging tests of this system.
A technique has been developed which permits toroidal, and coma-corrected toroidal, diffraction gratings to be replicated from spherical master gratings by the use of elastically-deformable substrates. Toroidal gratings correct for astigmatism and, thus, make it possible to construct stigmatic spectrometers that employ a single reflective diffraction grating. These spectrometers are particularly useful for the extreme-ultraviolet (EUV) wavelength range, where reflection coefficients are low, since the single optical surface provides for dispersion, focusing, and astigmatism correction. The fabrication procedures for the pure toroidal, and coma-corrected toroidal, gratings are described, and initial test results are presented. The use of the toroidal gratings in a high-resolution sounding-rocket EUV spectroheliometer, and in both the coronal diagnostics spectrometer and the ultraviolet coronagraph spectrometer on the ESA/NASA solar and heliospheric observatory mission, is described briefly, and the use of this technique for the fabrication of a coma-corrected toroidal grating for the prime Rowland spectrograph of the FUSE/Lyman mission is briefly discussed.
We describe the design of a high-resolution stigmatic extremeultraviolet (EUV) spectroheliometer, configured for flight on a Black Brant sounding rocket, which consists of a 45-cm Gregory telescope coupled to a spectrometer employing a single toroidal diffraction grating in a normalincidence Rowland circle mounting and an imaging pulse-counting multianode microchannel array (MAMA) detector system. The toroidal diffraction grating is fabricated by a technique employing an elastically deformable submaster grating that is replicated in a spherical form and then mechanically distorted to produce the desired aspect ratio of the toroidal surface for stigmatic imaging over the selected wavelength range. The spectroheliometer will produce spatially resolved spectra of the chromosphere, transition region, and corona with an angular resolution of 0.4 arcsec or better, a spectral resolution λ/Δλ of about 104 in first order, and a temporal resolution of the order of seconds. Because of the geometric fidelity of the MAMA detector system, the spectroheliometer will be able to determine Doppler shifts to a resolution of at least 2 mÅ at wavelengths near 600 Å (~1.0 km s-1), depending on the level of the accumulated signal. The unique characteristics of the spectroheliometer will be used in combination with plasma-diagnostic techniques to study the emperature, density, and velocity structures of specific features in the solar outer atmosphere.
We describe the design of a high-resolution stigmatic extreme-ultraviolet (EUV) spectroheliometer, configured for flight on a
Black Brant sounding rocket, which consists of a 45-cm Gregory telescope coupled to a spectrometer employing a single
toroidal diffraction grating in a normal-incidence Rowland circle mounting and an imaging pulse-counting Multi-Anode
Microchannel Array (MAMA) detector system. The toroidal diffraction grating is fabricated by a new technique employing an
elastically-deformable sub-master grating which is replicated in a spherical form and then mechanically distorted to produce the
desired aspect ratio of the toroidal surface for stigmatic imaging over the selected wavelength range. The spectroheliometer will
produce spatially-resolved spectra of the chromosphere, transition-region and corona with an angular resolution of 0.4 arc sec or
better, a spectral resolution AII of about 1O in first order, and a temporal resolution of the order of seconds. Because of the
geometric fidelity of the MAMA detector system, the speciroheliometer will be able to determine Doppler shifts to a resolution
of at least 2 mA at wavelengths near 600 A (-1.0 km s1), depending on the level of the accumulated signal. The unique
characteristics of the spectroheliometer will be used in combination with plasma-diagnostic techniques to study the temperature,
density and velocity structures of specific features in the solar outer atmosphere.
Current uses of the MAMA detector which utilize the photon time-tagging capabilities of these detectors are reported. These applications currently include image stabilization by means of post-processing corrections of platform drift and speckle interferometry. The initial results of a sounding rocket experiment to obtain UV images of NGC 6240 and results from speckle interferometry of Neptune's moon Triton are presented.
Imaging multianode microchannel array (MAMA) detector systems with 1024 x 1024 pixel formats have been produced for visible and UV wavelengths; the UV types employ 'solar blind' photocathodes whose detective quantum efficiencies are significantly higher than those of currently available CCDs operating at far-UV and EUV wavelengths. Attention is presently given to the configurations and performance capabilities of state-of-the-art MAMA detectors, with a view to the development requirements of the hybrid electronic circuits needed for forthcoming spacecraft-sensor applications. Gain, dark noise, uniformity, and dynamic range performance data are presented for the curved-channel 'chevron', 'Z-plate', and helical-channel high gain microchannel plate configurations that are currently under evaluation with MAMA detector systems.
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