The Rapid Transient Surveyor (RTS) is a proposed rapid-response, high-cadence adaptive optics (AO) facility for the UH 2.2-m telescope on Maunakea. RTS will uniquely address the need for high-acuity and sensitive near-infrared spectral follow-up observations of tens of thousands of objects in mere months by combining an excellent observing site, unmatched robotic observational efficiency, and an AO system that significantly increases both sensitivity and spatial resolving power. We will initially use RTS to obtain the infrared spectra of ∼4,000 Type Ia supernovae identified by the Asteroid Terrestrial-Impact Last Alert System over a two year period that will be crucial to precisely measuring distances and mapping the distribution of dark matter in the z < 0.1 universe. RTS will comprise an upgraded version of the Robo-AO laser AO system and will respond quickly to target-of-opportunity events, minimizing the time between discovery and characterization. RTS will acquire simultaneous-multicolor images with an acuity of 0.07–0.10" across the entire visible spectrum (20% i′-band Strehl in median conditions) and <0.16" in the near infrared, and will detect companions at 0.5" at contrast ratio of ∼500. The system will include a high-efficiency prism integral field unit spectrograph: R = 70-140 over a total bandpass of 840–1830nm with an 8.7" by 6.0" field of view (0.15" spaxels). The AO correction boosts the infrared point-source sensitivity of the spectrograph against the sky background by a factor of seven for faint targets, giving the UH 2.2-m the H-band sensitivity of a 5.7-m telescope without AO.
We will report on the on-sky, on-CCD, tip-tilt image compensation performance of GPC1, the 1.4 gigapixel mosaic focal
plane CCD camera for wide field surveys with a 7 square degree field of view. The camera uses 60 Orthogonal Transfer
Arrays (OTAs) with a novel 4 phase pixel architecture and the STARGRASP controller for closed loop multi-guide star
centroiding and image correction. The Pan-STARRS project is also constructing GPC2, the second 1.4 gigapixel camera
using 64 OTAs. GPC2 will include design enhancements over GPC1 including a new generation of OTAs, titanium
mosaic focal plane with adjustable three point kinematic mounts, cyro flex wiring and the recent software distributed
over 32 controllers. We will discuss the design, cost, schedule, tools developed, shortcomings and future plans for the
two largest digital cameras in the world.
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 24<sup>th</sup> 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 Pan-STARRS project has completed its first 1.4 gigapixel mosaic focal plane CCD camera, Gigapixel Camera #1
(GPC1). The mosaic focal plane of 60 densely packed 4k×4k MITLL CCD Orthogonal Transfer Arrays (OTAs)
constitutes the World's largest CCD camera. The camera represents an extremely cost and time efficient effort with a
less than 18 month production and integration phase and an approximate cost of $4 million USD (excluding NRE). The
controller electronics named STARGRASP was developed to handle the 480 outputs at near 1Mpixel/sec rates with
Gigabit Ethernet interfaces and can be scaled to even larger focal planes. Sophisticated functionality was developed for
guide readout and on-detector tip-tilt image compensation with selectable region logic for standby or active operation,
high output count, close four side buttable packaging and deep depletion construction. We will discuss the performance
achieved, on-sky results, design, tools developed, shortcomings and future plans.
The Pan-STARRS project has completed its first 1.4 gigapixel mosaic focalplane CCD camera using 60 Orthogonal Transfer
Arrays (OTAs). The devices are the second of a series of planned development lots. Several novel properties were
implemented into their design including 4 phase pixels for on-detector tip-tilt image compensation, selectable region logic
for standby or active operation, relatively high output amplifier count, close four side buttable packaging and deep depletion
construction. The testing and operational challenges of deploying these OTAs required enhancements and new approaches
to hardware and software. We compare performance achieved with that which was predicted, and discuss on-sky results,
tools developed, shortcomings, and plans for future OTA features and improvements.
The goal of this project is to achieve exquisite image quality over the largest possible field of view, with a goal of a
FWHM of not more than 0.3" over a square degree field in the optical domain. The narrow PSF will allow detection of
fainter sources in reasonable exposure times. The characteristics of the turbulence of Mauna Kea, a very thin ground
layer with excellent free seeing allows very wide fields to be corrected by GLAO and would make such an instrument
unique. The Ground Layer AO module uses a deformable mirror conjugated to the telescope pupil. Coupled with a high
order WFS, it corrects the turbulence common to the entire field. Over such large fields the probability of finding
sufficiently numerous and bright natural guide sources is high, but a constellation of laser beacons could be considered
to ensure homogeneous and uniform image quality.
The free atmosphere seeing then limits the image quality (50% best conditions: 0.2" to 0.4"). This can be further
improved by an OTCCD camera, which can correct local image motion on isokinetic scales from residual high altitude
tip-tilt. The advantages of the OTCCD are not limited to improving the image quality: a Panstarrs1 clone covers one
square degree with 0.1" sampling, in perfect accordance with the scientific requirements. The fast read time (6 seconds
for 1.4 Gpixels) also leads to an improvement of the dynamic range of the images. Finally, the guiding capabilities of
the OTCCD will provide the overall (local and global) tip-tilt signal.
Recent development efforts on the orthogonal transfer array (OTA) for the Pan-STARRS gigapixel camera 1 (GPC1) are described. A redesign of the prototype OTAs has been completed, and fabrication and packaging of the devices for the GPC1 are nearly complete. We briefly review the final design features and the resolution of the performance issues that arose in the first prototype devices. We then describe the packaging of the device and the challenges arising in achieving the necessary flatness at the device operating temperature. Plans and schedule for deploying focal-plane arrays of these devices are described.
Historically, few astronomical measurements have required sub-percent accuracy in photometry. Measuring SNIa fluxes
in order to determine cosmological parameters, however, often requires the comparison of images from different
telescopes, and at different redshifts. This can introduce a myriad of sources of error. Conventional methods of data
reduction are intrinsically flawed, either making assumptions about the effects of wavelength dependence in the response
function of the system or, when K-corrections are not performed, neglecting them altogether. We consider the
advantages of a method utilizing a direct, spectrally-resolved measurement of the entire system's response function
relative to a calibrated photodiode.
The orthogonal-transfer array (OTA) is a new charge-coupled device (CCD) concept for wide-field imaging in groundbased astronomy based on the orthogonal-transfer CCD (OTCCD). This device combines an 8×8 array of small OTCCDs, each about 600×600 pixels with on-chip logic to provide independent control and readout of each CCD. The device provides spatially varying electronic tip-tilt correction for wavefront aberrations, as well as compensation for telescope shake. Tests of prototype devices have verified correct functioning of the control logic and demonstrated good CCD charge-transfer efficiency and high quantum efficiency. Independent biasing of the substrate down to -40 V has enabled fully depleted operation of 75-μm-thick devices with good charge PSF. Spurious charge or "glow" due to impact ionization from high fields at the drains of some of the NMOS logic FETs has been observed, and reprocessing of some devices from the first lot has resolved this issue. Read noise levels have been 10 - 20 e-, higher than our goal of 5 e-, but we have identified the likely sources of the problem. A second design is currently in fabrication and uses a 10-μm pixel design resulting in a 22.6-Mpixel device measuring 50×50 mm. These devices will be deployed in the U. of Hawaii Pan-STARRS focal plane, which will comprise 60 OTAs with a total of nearly 1.4 Gpixels.
The orthogonal-transfer array (OTA) is a new CCD architecture designed to provide wide-field tip-tilt correction of astronomical images. The device consists of an 8x8 array of small (~500x500 pixels) orthogonal-transfer CCDs (OTCCD) with independent addressing and readout of each OTCCD. This approach enables an optimum tip-tilt correction to be applied independently to each OTCCD across the focal plane. The first design of this device has been carried out at MIT Lincoln Laboratory in support of the Pan-STARRS program with a collaborative parallel effort at Semiconductor Technology Associates (STA) for the WIYN Observatory. The two versions of this device are functionally compatible and share a common pinout and package. The first wafer lots are complete at Lincoln and at Dalsa and are undergoing wafer probing.
The PanSTARRS project has undertaken an ambitious effort to develop a completely new array controller architecture that is fundamentally driven by the large 1gigapixel, low noise, high speed OTCCD mosaic requirements as well as the size, power and weight restrictions of the PanSTARRS telescope. The result is a very small form factor next generation controller scalar building block with 1 Gigabit Ethernet interfaces that will be assembled into a system that will readout 512 outputs at ~1 Megapixel sample rates on each output. The paper will also discuss critical technology and fabrication techniques such as greater than 1MHz analog to digital converters (ADCs), multiple fast sampling and digital calculation of multiple correlated samples (DMCS), ball grid array (BGA) packaged circuits, LINUX running on embedded field programmable gate arrays (FPGAs) with hard core microprocessors for the prototype currently being developed.
The Space Interferometry Mission (SIM) spacecraft will be used to measure the proper motions for a sample of ~30 nearby galaxies. At this time there are no proper motion measurements of galaxies beyond the satellite systems of the Milky Way. With the capability of measuring absolute positions to 4 mas (microarcsecond) accuracy and a five-year baseline, SIM will be able to measure proper motions as small as 10 km/s over the Local Group and 40 km/s at 4 Mpc. The motion of each galaxy will be monitored by targeting 5-10 stars that are brighter than 20th magnitude. SIM measurements will lead to knowledge of the full 6-dimensional position and velocity vectors of each galaxy. In conjunction with gravitational flow modeling, improved total mass measurements of individual galaxies and the fractional contribution of dark matter to galaxies of the Local Group will be obtained. The project includes development of theoretical methods for orbital calculations.
The WIYN One Degree Imager (ODI) will be a well-sampled (0.11” per pixel) imager that provides a full one degree square field of view (32K×32K pixels). ODI will utilize high resistivity, red sensitive, orthogonal transfer (OT) CCDs to provide rapid correction for image motion arising from telescope shake, guider errors, and atmospheric effects. ODI will correct the full field of view by deploying 64 array packages having a total of 4096 independently controllable OTCCDs that can correct individually for local (2 arcmin) image motion. Each array package is an orthogonal transfer array (OTA) of 64 CCDs arranged in an 8×8 grid. Each CCD has 512×512 pixels. We expect the median image quality at the WIYN 3.5m telescope in RIZ to be 0.52”, 0.43”, and 0.35” FWHM. ODI makes optimal use of the WIYN telescope, which has superb optics, excellent seeing characteristics, a natural 1.4 degree field of view (with a new corrector), and can serve as a pathfinder for LSST in terms of detectors, data pipelines, operations strategies, and scientific motivation.
The IFA and collaborators are embarking on a project to develop a 4-telescope synoptic survey instrument. While somewhat smaller than the 6.5m class telescope envisaged by the decadal review in their proposal for a LSST, this facility will nonetheless be able to accomplish many of the LSST science goals. In this paper we will describe the motivation for a 'distributed aperture' approach for the LSST, the current concept for Pan-STARRS -- a pilot project for the LSST proper -- and its performance goals and science reach. We will also discuss how the facility may be expanded.
We describe progress in removing image motion over large fields of view. A camera using a new type of CCD has been commissioned and we report first results which are very promising for wide field imaging. We are embarking on a project to build a new type of astronomical CCD which should provide image motion compensation over arbitrarily large fields of view, very fast readout, autoguiding capability, good red sensitivity, and should be significantly less expensive than the present generation of CCDs.
We have entered an era of large CCD mosaic camera construction with many observatories developing large mosaic focal planes for wide field cameras and spectrographs. In this review, we outline the history of CCD mosaic development, describe the current state of the art while illustrating the many projects underway, and attempt to peer into the future.
We describe recent results from a new type of CCD imager which is capable of transferring charge in all four directions and is called an orthogonal-transfer CCD or OTCCD. This device has applications in adaptive imaging where the image motion is fast in relation to the frame time. We have built a 512 X 512 pixel frame-transfer device in which the imaging section has OT pixels and the frame store has conventional three-phase pixels. We have demonstrated at the Michigan-Dartmouth-MIT (MDM) observatory on Kitt Peak that significant improvements in seeing can be obtained by partially correcting for atmosphere-induced phase distortions using this device. By imaging a bright guide star on the frame store and operating it as a fast- framing tracker we are able to measure the lowest-order distortion. We then use this information to clock the OT section to maintain registration between the charge packets and the shifting star images. The preliminary results show that the OTCCD can remove approximately 0.5 inches in quadrature with the remaining sources of broadening at MDM. Pockets are more numerous in this device than expected, and their effects are exacerbated by the multiple transfers during image tracking. Some evidence has been found that links the pockets to the use of aluminum as the fourth gate level.