We only began to detect other planetary systems with the discovery of debris disks in 1983 with IRAS, followed by the great success of gravitational recoil measurements starting in 1995. We now know of many hundreds of them. Despite the phenomenal growth of this new field of study, our knowledge of each system is meager, strongly conditioned by observational limitations. In addition, our grasp of the ensemble properties is weak because of strong selection effects in the known samples. A series of new capabilities - Herschel, Kepler, WISE, SIM Planetquest, and JWST - will provide a systematic understanding by 2018, marking the 35th anniversary of the first IRAS detections. Specifically, we should have a good census of solar-type stars in habitable zones, a far better understanding of the evolution of terrestrial planets, and direct detections of a number of gas giants as well as new insights to their frequent migration into orbits very close to their stars and the consequences of this process for planetary systems in general.

The "big question" that the average person will ask an astronomer today is, "Are there Earth-like planets?" followed immediately by "Is there life on those planets?" We live in an age when we are privileged to be able to ask such a question, and have a reasonable expectation of receiving an answer, at least within the coming decade. As astronomers and physicists we are even more privileged to be the people who can provide those answers. This paper discusses the roles of four space missions that are planned by NASA to search for and characterize extrasolar planets: Kepler, Space Interferometer Mission (SIM-PlanetQuest), Terrestrial Planet Finder Coronagraph (TPF-C), and Terrestrial Planet finder Interferometer (TPF-I). The Kepler and SIM-PlanetQuest missions will search for and discover planets down to the few-Earth size and mass, around distant and nearby stars respectively. In favorable cases they will even be able to find Earth-size or mass planets. But to answer the questions "is a given planet habitable?" and "does it show signs of life?" we will need the TPF-C and TPF-I missions. Only these missions can isolate the light of the planet from the confusion of otherwise blinding starlight, and only these missions can perform spectroscopy on the planets. Visible and thermal infrared spectroscopy together will tell us if a planet is habitable and shows signs of life. TPF-C and TPF-I will build on the legacy of Kepler and SIM-PlanetQuest, and together these four missions will provide complete and unambiguous answers to our "big questions." This paper concentrates on the TPF-C mission.

The NASA Advanced Telescope and Observatory (ATO) Capability Roadmap addresses technologies necessary for NASA to enable future space telescopes and observatories operating in all electromagnetic bands, from x-rays to millimeter waves, and including gravity-waves. It lists capability priorities derived from current and developing Space Missions Directorate (SMD) strategic roadmaps. Technology topics include optics; wavefront sensing and control and interferometry; distributed and advanced spacecraft systems; cryogenic and thermal control systems; large precision structure for observatories; and the infrastructure essential to future space telescopes and observatories. This paper summarizes optic technology capability requirements necessary to enable space telescopes from the UV to Far-Infared.

The Science Programme of the European Space Agency (ESA) for the next decade is currently being defined, and it is expected that the first steps in its implementation will be taken in the coming year. The technology developments required will necessarily depend on this Program: Cosmic Visions 2015-2025 [1]. However for any suite of potential missions, the timely and systematic development of key technologies will be crucial for its success. While the details of the technologies required will mature as the programme and mission characteristics become clearer, it is still possible to identify at an early stage many of the key developments. In addition it is also possible to identify those technologies, which may be common to a number of potential future science missions. For example; large aperture deployable mirror systems are a common requirement for astrophysics-type missions although the design details differ significantly depending on wavelength. Another example is European-based near infrared sensor array technology, which embraces many areas of space science.

We provide an overview of the design of the Spitzer Space Telescope and review scientific highlights from the first 30 months of on-orbit operations.

During the expected 5+ years of operation, the Spitzer Space Telescope is and will continue to produce outstanding infrared images and spectra, and greatly further scientific understanding of our universe. The Spitzer Space Telescope's instruments are cryogenically cooled to achieve low dark current and low noise. After the cryogens are exhausted, the Spitzer Space Telescope will only be cooled by passively radiating into space. The detector arrays in the IRAC instrument are expected to equilibrate at approximately 30K. The two shortest wavelength channels (3.6 and 4.5 micron) employ InSb detector arrays and are expected to function and perform with only a modest degradation in sensitivity. Thus, an extended mission is possible for Spitzer. We present the predicted dark current, noise, quantum efficiency and image residuals for the 3.6 and 4.5 micron IRAC channels in the post-cryogen era.

SPIRE, the Spectral and Photometric Imaging Receiver, is a submillimetre camera and spectrometer for the European Space Agency's Herschel Space Observatory. It comprises a three-band imaging photometer operating at 250, 360 and 520 μm, and an imaging Fourier Transform Spectrometer (FTS) covering 200-670 μm. The detectors are arrays of feedhorn-coupled NTD spider-web bolometers cooled to 0.3 K. The photometer field of view of is 4 x 8 arcmin., observed simultaneously in the three spectral bands. The FTS has an approximately circular field of view with a diameter of 2.6 arcmin., and employs a dual-beam configuration with broad-band intensity beam dividers to provide high efficiency and separated output and input ports. The spectral resolution can be adjusted between 0.04 and 2 cm-1 (resolving power of 20-1000 at 250 μm). The flight instrument is currently undergoing integration and test. The design of SPIRE is described, and the expected scientific performance is summarised, based on modelling and flight instrument test results.

The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments for ESA's far infrared and submillimeter observatory Herschel. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 × 25 pixels, each, and two filled silicon bolometer arrays with 16 × 32 and 32 × 64 pixels, respectively, to perform imaging line spectroscopy and imaging photometry in the 60-210μm wavelength band. In photometry mode, it will simultaneously image two bands, 60-85μm or 85-130μm and 130-210μm, over a field of view of ~ 1.75' × 3.5', with full beam sampling in each band. In spectroscopy mode, it will image a field of ~50"×50", resolved into 5×5 pixels, with an instantaneous spectral coverage of ~1500 km/s and a spectral resolution of ~ 175 km/s. In both modes the performance is expected to be not far from background-noise limited, with sensitivities (5σ in 1h) of ~ 4 mJy or 3 - 20 ×10^-18W/m², respectively. We summarize the design of the instrument and its subunits, describe the observing modes in combination with the telescope pointing modes, report results from instrument level performance tests of the Qualification Model, and present our current prediction of the in-orbit performance of the instrument based on tests done at subunit level.

The development program of the flight model imaging camera for the PACS instrument on-board the Herschel spacecraft is nearing completion. This camera has two channels covering the 60 to 210 microns wavelength range. The focal plane of the short wavelength channel is made of a mosaic of 2×4 3-sides buttable bolometer arrays (16×16 pixels each) for a total of 2048 pixels, while the long wavelength channel has a mosaic of 2 of the same bolometer arrays for a total of 512 pixels. The 10 arrays have been fabricated, individually tested and integrated in the photometer. They represent the first filled arrays of fully collectively built bolometers with a cold multiplexed readout, allowing for a properly sampled coverage of the full instrument field of view. The camera has been fully characterized and the ground calibration campaign will take place after its delivery to the PACS consortium in mid 2006. The bolometers, working at a temperature of 300 mK, have a NEP close to the BLIP limit and an optical bandwidth of 4 to 5 Hz that will permit the mapping of large sky areas. This paper briefly presents the concept and technology of the detectors as well as the cryocooler and the warm electronics. Then we focus on the performances of the integrated focal planes (responsivity, NEP, low frequency noise, bandwidth).

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space Observatory. The instrument covers 200 to 670 μm with a three band photometric camera and a two band imaging Fourier Transform Spectrometer (IFTS). In this paper we discuss the performance of the optics of the instrument as determined during the pre-flight instrument testing to date. In particular we concentrate on the response of the instrument to a point source, the comparison between the visible light alignment and the infrared alignment and the effect of the optical performance on the overall instrument sensitivity. We compare the empirical performance of the instrument optics to that expected from elementary diffraction theory.

The Spectral and Photometric Imaging REceiver (SPIRE) is one of the three scientific instruments to fly on the European Space Agency's Herschel Space Observatory, and contains a three-band imaging submillimetre photometer and an imaging Fourier transform spectrometer. The flight model of the SPIRE cold focal plane unit has been built up in stages with a cold test campaign associated with each stage. The first campaign focusing on the spectrometer took place in early 2005 and the second campaign focusing on the photometer was in Autumn 2005. SPIRE is currently undergoing its third cold test campaign following cryogenic vibration testing. Test results to date show that the instrument is performing very well and in general meets not only its requirements but also most of its performance goals. We present an overview of the instrument tests performed to date, and the preliminary results.

In this paper we present the test results of the qualification model (QM) of the LFI instrument, which is being developed as part of the ESA Planck satellite. In particular we discuss the calibration plan which has defined the main requirements of the radiometric tests and of the experimental setups. Then we describe how these requirements have been implemented in the custom-developed cryo-facilities and present the main results. We conclude with a discussion of the lessons learned for the testing of the LFI Flight Model (FM).

The core of the High Frequency Instrument (HFI) on-board the Planck satellite consists of 52 bolometric detectors cooled at 0.1 Kelvin. In order to achieve such a low temperature, the HFI cryogenic architecture consists in several stages cooled using different active coolers. These generate weak thermal fluctuations on the HFI thermal stages. Without a dedicated thermal control system these fluctuations could produce unwanted systematic effects, altering the scientific data. The HFI thermal architecture allows to minimise these systematic effects, thanks to passive and active control systems described in this paper. The passive and active systems are used to damp the high and low frequency fluctuations respectively. The last results regarding the tests of the HFI passive and active thermal control systems are presented here. The thermal transfer functions measurement between active coolers and HFI cryogenic stages will be presented first. Then the stability of the temperatures obtained on the various cryogenic stages with PID regulations systems will be checked through analysis of their power spectrum density.

Wide Field Camera 3 (WFC3) is a powerful UV/visible/near-infrared camera currently in development for installation into the Hubble Space Telescope. WFC3 provides two imaging channels. The UVIS channel features a 4096 x 4096 pixel CCD focal plane covering 200 to 1000 nm wavelengths with a 160 x 160 arcsec field of view. The UVIS channel provides unprecedented sensitivity and field of view in the near ultraviolet for HST. It is particularly well suited for studies of the star formation history of local galaxies and clusters, searches for Lyman alpha dropouts at moderate redshift, and searches for low surface brightness structures against the dark UV sky background. The IR channel features a 1024 x 1024 pixel HgCdTe focal plane covering 800 to 1700 nm with a 139 x 123 arcsec field of view, providing a major advance in IR survey efficiency for HST. IR channel science goals include studies of dark energy, galaxy formation at high redshift, and star formation. The instrument is being prepared for launch as part of HST Servicing Mission 4, tentatively scheduled for late 2007, contingent upon formal approval of shuttle-based servicing after successful shuttle return-to-flight. We report here on the status and performance of WFC3.

Wide Field Camera 3 (WFC3), a panchromatic imager being developed for the Hubble Space Telescope (HST), is now fully integrated and has undergone extensive ground testing at Goddard Space Flight Center, in both ambient and thermal-vacuum test environments. The thermal-vacuum testing marks the first time that both of the WFC3 UV/Visible and IR channels have been operated and characterized in flight-like conditions. The testing processes are completely automated, with WFC3 and the optical stimulus that is used to provide external targets and sources being commanded by coordinated computer scripts. All test data are captured and stored in the long-term Hubble Data Archive. A full suite of instrument calibration tests have been performed, including measurements of detector properties such as dark current, read noise, flat field response, gain, linearity, and persistence, as well as total system throughput, encircled energy, grism dispersions, IR thermal background, and image stability tests. Nearly all instrument characteristics have been shown to meet or exceed expectations and requirements. Solutions to all issues discovered during testing are in the process of being implemented and will be verified during future ground tests.

The proposed JAXA/ISAS SPICA mission will have a cooled 3.5 m mirror and will be the next step forward in sensitivity in far infrared astronomy. We describe the scientific case for an imaging Far Infrared Spectrometer for the SPICA mission and the ongoing design study being carried out by European scientists.

The scientific capabilities of the James Webb Space Telescope (JWST) fall into four themes. The End of the Dark Ages: First Light and Reionization theme seeks to identify the first luminous sources to form and to determine the ionization history of the universe. The Assembly of Galaxies theme seeks to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present. The Birth of Stars and Protoplanetary Systems theme seeks to unravel the birth and early evolution of stars, from infall onto dust-enshrouded protostars, to the genesis of planetary systems. Planetary Systems and the Origins of Life theme seeks to determine the physical and chemical properties of planetary systems around nearby stars and of our own, and investigate the potential for life in those systems. To enable these for science themes, JWST will be a large (6.5m) cold (50K) telescope with four instruments, capable of imaging and spectroscopy from 0.6 to 29 microns wavelength.

The CorECam Instrument Concept Study (ICS) addressed the requirements and science program for the Terrestrial Planet Finder Coronagraph's (TPF-C) primary camera. CorECam provides a simple interface to TPF-C's Starlight Suppression System (SSS) which would be provided by the TPF-C Program, and comprises camera modules providing visible, and near-infrared (NIR) camera focal plane imaging. In its primary operating mode, CorECam will conduct the core science program of TPF-C, detecting terrestrial planets at visible wavelengths. CorECam additionally provides the imaging capabilities to characterize terrestrial planets, and conduct an extended science program focused on investigating the nature of the exosolar systems in which terrestrial planets are detected. In order to evaluate the performance of CorECam we developed a comprehensive, end-to-end model using OSCAR which has provided a number of key conclusions on the robustness of the TPF-C baseline design, and allows investigation of alternative techniques for wavefront sensing and control. CorECam recommends photon counting detectors be baselined for imaging with TPF-C since they provide mitigations against the background radiation environment, improved sensitivity and facilitate alternative WFSC approaches.

The James Webb Space Telescope is a 6.5 meter segmented cryogenic telescope scheduled to be launched in 2013. A key development challenge has been the cost and complexity of cryogenic optical testing of the telescope and observatory. A new approach to cryogenic optical testing the telescope and observatory has been developed that eliminates the need for a complex and expensive cryogenic optical test tower and which also allows all critical test equipment to be external to the chamber and accessible during testing. This paper summarizes the motivation for this change, the conceptual design of it, and status of implementing it.

The unprecedented stability requirements of JWST structures can only be conclusively verified by a combination of analysis and ground test. Given the order of magnitude of the expected motions of the backplane due to thermal distortion and the high level of confidence required on such a large and important project, the demonstration of the ability to verify the thermal distortion analysis to the levels required is a critical need for the program. The demonstration of these analysis tools, in process metrology and manufacturing processes increases the technology readiness level of the backplane to required levels. To develop this critical technology, the Backplane Stability Test Article (BSTA) was added to the JWST program. The BSTA is a representative substructure for the full flight backplane, manufactured using the same resources, materials and processes. The BSTA will be subject to environmental testing and its deformation and damping properties measured. The thermally induced deformation will be compared with predicted deformations to demonstrate the ability to predict thermal deformation to the levels required. This paper will review the key features and requirements of the BSTA and its analysis, the test, measurement and data collection plans.

The one-meter Testbed Telescope (TBT) has been developed at Ball Aerospace to facilitate the design and implementation of the wavefront sensing and control (WFS&C) capabilities of the James Webb Space Telescope (JWST). The TBT is used to develop and verify the WFS&C algorithms, check the communication interfaces, validate the WFS&C optical components and actuators, and provide risk reduction opportunities for test approaches for later full-scale cryogenic vacuum testing of the observatory. In addition, the TBT provides a vital opportunity to demonstrate the entire WFS&C commissioning process. This paper describes recent WFS&C commissioning experiments that have been performed on the TBT.

The James Webb Space Telescope (JWST) is a large space based astronomical telescope that will operate at cryogenic temperatures. The architecture has the telescope exposed to space, with a large sun shield providing thermal isolation and protection from direct illumination from the sun. The instruments will have the capability to observe over a spectral range from 0.6μm to 29 μm wavelengths. The following paper will present the stray light analysis results characterizing the stray light getting to the instrument focal planes from the full galactic sky, zodiacal background, bright objects near the line of sight, and scattered earth and moon shine. The amount of self-generated infrared background from the Observatory that reaches the instrument focal planes will also be presented.

Significant progress has been made in the development of the Optical Telescope Element (OTE), one of three elements of the James Webb Space Telescope (JWST) Observatory. To achieve the 25 square meters of collecting area, JWST will employ the first segmented, deployed optical telescope, requiring a wavefront sensing and control (WFS&C) system to align and phase the telescope's optics, while operating at cryogenic temperatures. The OTE is comprised of the optical components of the three mirror anastigmat and a steering mirror, the structure to deploy and support the optics, the WFS&C system to determine the adjustments necessary to align them, the electronics to control them, and the thermal components to manage the OTE temperatures. Technology development and risk reduction hardware are being produced to address critical technical areas. Subsystem development has progressed with the successful completion of several key design reviews and significant progress on the production of the flight Primary Mirror Segment Assemblies.

We present concepts for the background-limited infrared-submillimeter spectrograph (BLISS) for the Japanese SPICA mission to launch early next decade. SPICA will be a 3.5-meter telescope cooled to below 5 K, and offers the potential for far-IR observations limited only by the zodiacal dust emission. BLISS will provide moderate-resolution (R 1000) spectroscopy at this background limit throughout the 40-600 μm band. With sensitivities below 10^-20 Wm² in modest integrations, BLISS-SPICA will enable the first survey spectroscopy of the redshift 0.5 to 5 galaxies which produce the far-IR background. Both WaFIRS waveguide grating spectrometers, and new compact cross-dispersed echelle grating designs are under consideration. Detectors must have sensitivities around 3x10^-20 W/√Hz and have good efficiency. The most promising near-term approaches to cover the full band are transition-edge bolometers cooled to ~50 mK with an adiabatic demagnetization refrigerator.

The context, preparation, and facilitization of Tinsley to produce the 18 JWST primary mirror segments are described, and an overview of the Project at Tinsley is presented. The mirror segments are aggressively lightweighted, approximately hexagonal, and approximately 1.32m flat-to-flat. While the optical finishing approach is strongly seated in Tinsley's Computer Controlled Optical Surfacing (CCOS^TM) technology, extensions have been implemented to address safe and efficient nearly simultaneous flow of the high value mirror segments through numerous cycles of optical finishing, processing and metrology steps. JWST will operate at cryogenic temperatures, and Tinsley will do final figuring from a "hit map" made during cryogenic testing at the NASA MSFC X-Ray Calibration Facility (XRCF). A formal beryllium safety protocol has been established throughout. Extensive handling fixtures assure that the mirrors are moved from station to station experiencing low accelerations. A rigorous qualification process is applied to each new fixture, machine and instrument. Special problems of cryo figuring, and co-finishing the segments to stringent specifications are described.

We describe software which models the Point Spread Function of the James Webb Space Telescope. The software is designed to be expandable to incorporate optical and instrument data as they become available. An initial model of the detector used in the Near Infra-red Camera has been used to generate realistic stellar images.

From its orbit around the Earth-Sun second Lagrange point some million miles from Earth, the James Webb Space Telescope (JWST) will be uniquely suited to study early galaxy and star formation with its suite of infrared instruments. To maintain exceptional image quality using its 6.6 meter segmented primary mirror, wavefront sensing and control (WFS&C) is vital to ensure the optical alignment of the telescope throughout the mission. WFS&C design architecture includes using the Near-Infrared Camera (NIRCam) to provide imagery for ground-resident image processing algorithms which determine the optimal alignment of the telescope. There are two distinct mission phases for WFS&C, both of which use algorithms and NIRCam imagery to determine the required segment updates. For the first phase, WFS&C commissioning, the telescope is taken from its initial deployed state with each of the 18 primary mirror segments acting like independent telescopes, to its final phased state with each segment acting in concert as a part of a single mirror. The second phase, Wavefront Monitoring and Maintenance, continues for the rest of the mission. Here the wavefront quality is evaluated, and when needed, the mirror positions are updated to bring it back to an optimal configuration. This paper discusses the concept of operations for the commissioning and on-going maintenance of the telescope alignment using WFS&C.

Dispersed Fringe Sensing (DFS) is an efficient and robust method for coarse phasing of a segmented primary mirror such as the James Webb Space Telescope (JWST). In this paper, modeling and simulations are used to study the effect of segmented mirror aberrations on the DFS fringe image, its signals, and the piston detection accuracy. The simulations show that due to the pixilation spatial filter effect from DFS signal extraction the effect of wavefront error is reduced. In addition, the DFS algorithm is more robust against wavefront aberration when the multi-trace DFS approach is used. We have also studied the JWST Dispersed Hartmann Sensor (DHS) performance in presence of wavefront aberrations caused by the gravity sag and we have used the scaled gravity sag to explore the JWST DHS performance relationship with the level of the wavefront aberration. As a special case of aberration we have also included the effect from line-of-sight jitter in the JWST modeling study.

The James Webb Space Telescope (JWST) Coarse Phase Sensor utilizes Dispersed Hartmann Sensing (DHS)¹ to measure the inter-segment piston errors of the primary mirror. The DHS technique was tested on the Keck Telescope. Two DHS optical components were built to mate with the Keck optical and mechanical interfaces. DHS images were acquired using 20 different primary mirror configurations. The mirror configurations consisted of random segment pistons applied to 18 of the 36 segments. The inter-segment piston errors ranged from phased (approximately 0 μm) to as large as ±25 μm. Two broadband exposures were taken for each primary mirror configuration: one for the DHS component situated at 0°, and one for the DHS component situated at 60°. Finally, a "closed-loop" DHS sensing and control experiment was performed. Sensing algorithms developed by both Adaptive Optics Associates (AOA) and the Jet Propulsion Laboratory (JPL)² were applied to the collected DHS images. The inter-segment piston errors determined by the AOA and JPL algorithms were compared to the actual piston steps. The data clearly demonstrates that the DHS works quite well as an estimator of segment-to-segment piston errors using stellar sources.

The James Webb Space Telescope (JWST) is a large space based astronomical telescope employing a primary mirror constructed of 18 hexagonal segments to create its large collecting area, and an image based wavefront sensor at the telescope focal plane to provide knowledge of system alignment. The combination of image sensing at the focal plane over a subset of the telescope's field of view and the resolution of the wavefront sensing system gives rise to a global alignment ambiguity between the primary and secondary mirror. This paper describes the possible magnitude of wavefront error impact outside the alignment region of the FOV for various global alignment modes under the constraint of the various ambiguity limiting factors at the currently estimated wavefront sensing resolution limit.

An image-based wavefront sensing and control algorithm for the James Webb Space Telescope (JWST) is presented. The algorithm heritage is discussed in addition to implications for algorithm performance dictated by NASA's Technology Readiness Level (TRL) 6. The algorithm uses feedback through an adaptive diversity function to avoid the need for phase-unwrapping post-processing steps. Algorithm results are demonstrated using JWST Testbed Telescope (TBT) commissioning data and the accuracy is assessed by comparison with interferometer results on a multi-wave phase aberration. Strategies for minimizing aliasing artifacts in the recovered phase are presented and orthogonal basis functions are implemented for representing wavefronts in irregular hexagonal apertures. Algorithm implementation on a parallel cluster of high-speed digital signal processors (DSPs) is also discussed.

The James Webb Space Telescope (JWST) is a segmented deployable telescope that will require on-orbit alignment using the Near Infrared Camera as a wavefront sensor. The telescope will be aligned by adjusting seven degrees of freedom on each of 18 primary mirror segments and five degrees of freedom on the secondary mirror to optimize the performance of the telescope and camera at a wavelength of 2 microns. With the completion of these adjustments, the telescope focus is set and the optical performance of each of the other science instruments should then be optimal without making further telescope focus adjustments for each individual instrument. This alignment approach requires confocality of the instruments after integration and alignment to the composite metering structure, which will be verified during instrument level testing at Goddard Space Flight Center with a telescope optical simulator. In this paper, we present the results from a study of several analytical approaches to determine the focus for each instrument. The goal of the study is to compare the accuracies obtained for each method, and to select the most feasible for use during optical testing.

The Integrated Science Instrument Module of the James Webb Space Telescope is described from a systems perspective with emphasis on unique and advanced technology aspects. The major subsystems of this flight element are described including: structure, thermal, command and data handling, and software.

The MIRI Medium Resolution Spectrometer (MIRI-MRS) will increase the sensitivity of astronomical spectroscopy at thermal infrared wavelengths (from 5 to 28 microns), by a factor of 1000 over the best that can be achieved by existing ground-based instruments. This leap in performance is further enhanced by the first use at these wavelengths of all reflective Integral Field Units (image slicers) to provide the spectrometer with a rectangular field of view with a shortest dimension of 3.5 arcseconds. We describe the optical design of the MRS and present predictions for its delivered image quality.

The nulling coronagraph is one of 5 instrument concepts selected by NASA for study for potential use in the TPF-C mission. This concept for extreme starlight suppression has two major components, a nulling interferometer to suppress the starlight to ~10^-10 per airy spot within 2 λ/D of the star, and a calibration interferometer to measure the residual scattered starlight. The ability to work at 2 λ/D dramatically improves the science throughput of a space based coronagraph like TPF-C. The calibration interferometer is an equally important part of the starlight suppression system. It measures the measures the wavefront of the scattered starlight with very high SNR, to 0.05nm in less than 5 minutes on a 5mag star. In addition, the post coronagraph wavefront sensor will be used to measure the residual scattered light after the coronagraph and subtract it in post processing to 1~2x10^-11 to enable detection of an Earthlike planet with a SNR of 5~10.

The Shaped Pupil Coronagraph (SPC) is a high-contrast imaging system pioneered at Princeton for detection of extra-solar earthlike planets. It is designed to achieve 10-10 contrast at an inner working angle of 4λ/D. However, a critical requirement in attaining this contrast level in practice is the ability to control wavefront phase and amplitude aberrations to at least λ/10⁴ in rms phase and 1/1000 rms amplitude, respectively. Furthermore, this has to be maintained over a large spectral band. The High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Lab (JPL) is a state-of-the-art facility for studying high contrast imaging systems and fine wavefront control methods. It consists of a vacuum chamber containing a configurable coronagraph setup with a Xinetics deformable mirror. In this paper, we present the results of testing Princeton's SPC in JPL's HCIT. In particular, we present the achievement of 4x10^-8 contrast using a speckle nulling algorithm, and demonstrate that this contrast is maintained across wavelengths of 785, 836nm, and for broadband light having 10% bandwidth around 800nm.

We describe the advantages of a nulling coronagraph instrument behind a single aperture space telescope for detection and spectroscopy of Earth-like extrasolar planets in visible light. Our concept synthesizes a nulling interferometer by shearing the telescope pupil into multiple beams. They are recombined with a pseudo-achromatic pi-phase shift in one arm to produce a deep null on-axis, attenuating the starlight, while simultaneously transmitting the off-axis planet light. Our nulling configuration includes methods to mitigate stellar leakage, such as spatial filtering by a coherent array of single mode fibers, balancing amplitude and phase with a segmented deformable mirror, and post-starlight suppression wavefront sensing and control. With diffraction limited telescope optics and similar quality components in the optical train (λ/20), suppression of the starlight to 10-10 is readily achievable. We describe key features of the architecture and analysis, present the status of key experiments to demonstrate wide bandwidth null depth, and present the status of component technology development.

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F type stars which cannot be found with RV techniques, and observe the inner spatial structure and colors of debris disks. EPIC has a proposed launch date of 2012 to heliocentric Earth trailing drift-away orbit, with a 3 year mission lifetime (5 year goal), and will revisit planets at least three times at intervals of 9 months. The robust mission design is simple and flexible ensuring mission success while minimizing cost and risk. The science payload consists of a heritage optical telescope assembly (OTA), and visible nulling coronagraph (VNC) instrument. The instrument achieves a contrast ratio of 109 over a 4.84 arcsecond field-of-view with an unprecedented inner working angle of 0.14 arcseconds over the spectral range of 440-880 nm, with spectral resolutions from 10 - 150. The telescope is a 1.5 meter offaxis Cassegrain with an OTA wavefront error of λ/9, which when coupled to the VNC greatly reduces the requirements on the large scale optics, compressing them to stability requirements within the relatively compact VNC optical chain. The VNC features two integrated modular nullers, a spatial filter array (SFA), and an E2V-L3 photon counting CCD. Direct null control is accomplished from the science focal mitigating against complex wavefront and amplitude sensing and control strategies.

To detect Earth-like planets in the visible with a coronagraphic telescope, two major noise sources have to be overcome: the photon noise of the diffracted star light, and the speckle noise due to the star light scattered by instrumental defects. Coronagraphs tackle only the photon noise contribution. In order to decrease the speckle noise below the planet level, an active control of the wave front is required. We have developed analytical methods to measure and correct the speckle noise behind a coronagraph with a deformable mirror. In this paper, we summarize these methods, present numerical simulations, and discuss preliminary experimental results obtained with the High-Contrast Imaging Testbed at NASA's Jet Propulsion Laboratory.

Imaging for exo-planet detection requires both high contrast and a small inner working angle. We show that, for several of the techniques proposed so far to achieve this, the inner working angle can be reduced by adding pupil replication between the telescope and the high contrast imaging system. Using pupil replication, the on-axis image of the star is decreased to a size smaller than the diffraction limit of the telescope, and off axis the point spread function of the planet undergoes minor changes, contained within the envelope of the point spread function of the telescope; the spectrum remains unchanged. The principle of pupil replication was proven experimentally and can be effected by a small-sized, high throughput optical system added between the telescope and the high contrast imaging system. High contrast imaging systems to which pupil replication has been found to be applicable so far include apodisation techniques like pupil apodisation, aperture masks, image plane masks, coronagraphs and combinations. Mathematical assessment and simulations of the sensitivity of pupil replication to optical errors show that the requirements for this system are the same as those for the primary telescope - pupil replication effectively remaps the output pupil of the telescope to the input pupil of the high contrast imaging system. Our results in this paper aim to show, in a realistic set-up, the feasibility of an improvement of the inner working angle by a factor of 4 using four-fold replication optics while maintaining the contrast performance. We do this through analysis of the pupil replication principle including off axis behavior when applied to high contrast imaging systems using pupil apodisation or a shaped mask. We specifically look at the situations similar to that of the Terrestrial Planet Finder Coronagraph and Darwin. We found that an inner working angle of 30 mas can be achieved with a contrast of 10^-10 and a large field of view without increasing the requirements except for the pointing.

Pupil mapping, also known as phase induced amplitude apodization or PIAA, has emerged as an interesting design concept for NASA's Terrestrial Planet Finder space telescope. However, in a previous paper it was demonstrated that diffraction effects limit the best achievable contrast to about 10^-5, which is 5 orders of magnitude short of the required level. Recent work by Olivier Guyon and his collaborators shows that a certain hybrid system can restore the contrast to the required level without degrading significantly the attractive throughput, achromaticity, and inner working angle advantages. In this paper, efficient computational tools are described that can be used to evaluate such designs. It is shown that a design similar to the one proposed by Guyon does indeed meet the contrast requirement.

The Phase-Induced Amplitude Apodization Coronagraph (PIAAC) uses a lossless beam apodization, performed by aspheric mirrors, to produce a high contrast PSF. This concept offers a unique combination of high throughput (almost 100%), high angular resolution (λ/D), small inner working angle (IWA = 1.5 λ/D), excellent achromaticity (the apodization is performed by geometric reflection on mirrors) and low sensitivity to pointing errors or stellar angular diameter. These characteristics make the PIAAC an ideal choice for direct imaging of extrasolar terrestrial planets (ETPs) from space. We quantify the performance of the PIAAC and other coronagraph designs both in terms of "raw" coronagraphic performance (throughput, IWA etc...) and number of stars around which extrasolar terrestrial planets (ETPs) can be observed. We also identify the fundamental performance limit that can be achieved by coronagraphy, and show that no other coronagraph design is as close to this limit as the PIAAC. We find that in the photon noise limited regime, a 4m telescope with a PIAA coronagraph is able to detect Earth-like planets around 30 stars with 1hr exposure time per target (assuming 25% throughput and exozodi levels similar to our solar system). With a smaller 1 to 2-m diameter telescope, more massive rocky planets could be detected in the habitable zones of a few nearby stars, and an imaging survey of Jupiter-like planets could be performed. Laboratory results and detailed simulations confirm the large potential of this concept for direct imaging of ETPs. A prototype high contrast PIAAC system is currently being operated to demonstrate the coronagraph's performance.

Direct detection of planets around nearby stars requires the development of high-contrast imaging techniques, because of their very different respective fluxes. We thus investigated the innovative coronagraphic approach based on the use of a four-quadrant phase mask (FQPM). Simulations showed that, combined with high-level wavefront correction on an unobscured off-axis section of a large telescope, this method allows high-contrast imaging very close to stars, with detection capability superior to that of a traditional coronagraph. A FQPM instrument was thus built to test the feasibility of near-neighbor observations with our new off-axis approach on a ground-based telescope. In June 2005, we deployed our instrument to the Palomar 200-inch telescope, using existing facilities as much as possible for rapid implementation. In these initial observations, using data processing techniques specific to FQPM coronagraphs, we reached extinction levels of the order of 200:1. Here we discuss our simulations and on-sky results obtained so far.

We derive the requirements on the surface height uniformity and reflectivity uniformity of the Terrestrial Planet Finder Coronagraph telescope and instrument optics for spatial frequencies within and beyond the spatial control bandwidth of the wave front control system. Three different wave front control systems are considered: a zero-path difference Michelson interferometer with two deformable mirrors at a pupil image; a sequential pair of deformable mirrors with one placed at a pupil image; and the Visible Nuller spatially-filtered controller. We show that the optical bandwidth limits the useful outer working angle.

We report progress on the development of precision binary notch-filter focal plane coronagraphic masks for directly imaging Earth-like planets at visible wavelengths with the Terrestrial Planet Finder Coronagraph (TPF-C), and substellar companions at near infrared wavelengths from the ground with coronagraphs coupled to high-order adaptive optics (AO) systems. Our recent theoretical studies show that 8th-order image masks (Kuchner, Crepp & Ge 2005, KCG05) are capable of achieving unlimited dynamic range in an ideal optical system, while simultaneously remaining relatively insensitive to low-spatial-frequency optical aberrations, such as tip/tilt errors, defocus, coma, astigmatism, etc. These features offer a suite of advantages for the TPF-C by relaxing many control and stability requirements, and can also provide resistance to common practical problems associated with ground-based observations; for example, telescope flexure and low-order errors left uncorrected by the AO system due to wavefront sensor-deformable mirror lag time can leak light at significant levels. Our recent lab experiments show that prototype image masks can generate contrast levels on the order of 2x10^-6 at 3 λ/D and 6x10^-7 at 10 λ/D without deformable mirror correction using monochromatic light (Crepp et al. 2006), and that this contrast is limited primarily by light scattered by imperfections in the optics and extra diffraction created by mask construction errors. These experiments also indicate that the tilt and defocus sensitivities of high-order masks follow the theoretical predictions of Shaklan and Green 2005. In this paper, we discuss these topics as well as review our progress on developing techniques for fabricating a new series of image masks that are "free-standing", as such construction designs may alleviate some of the (mostly chromatic) problems associated with masks that rely on glass substrates for mechanical support. Finally, results obtained from our AO coronagraph simulations are provided in the last section. In particular, we find that: (i) apodized masks provide deeper contrast than hard-edge masks when the image quality exceeds 80% Strehl ratio (SR), (ii) above 90% SR, 4th-order band-limited masks provide higher off-axis throughput than Gaussian masks when generating comparable contrast levels, and (iii) below ~90% SR, hard-edge masks may be better suited for high contrast imaging, since they are less susceptible to tip/tilt alignment errors.

The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for a spacecraft-borne nulling interferometer for high-resolution astronomy and the direct detection of exoplanets and assay of their environments and atmospheres. FKSI is a high angular resolution system operating in the near to mid-infrared spectral region and is a scientific and technological pathfinder to the Darwin and Terrestrial Planet Finder (TPF) missions. The instrument is configured with an optical system consisting, depending on configuration, of two 0.5 - 1.0 m telescopes on a 12.5 - 20 m boom feeding a symmetric, dual Mach- Zehnder beam combiner. We report on progress on our nulling testbed including the design of an optical pathlength null-tracking control system and development of a testing regime for hollow-core fiber waveguides proposed for use in wavefront cleanup. We also report results of integrated simulation studies of the planet detection performance of FKSI and results from an in-depth control system and residual optical pathlength jitter analysis.

The space based mission Pegase was proposed to CNES in the framework of its call for scientific proposals for formation flying missions. This paper presents a summary of the phase-0 performed in 2005. The main scientific goal is the spectroscopy of hot Jupiters (Pegasides) and brown dwarfs from 2.5 to 5 μm. The mission can extend to other objectives such as the exploration of the inner part of protoplanetary disks, the study of dust clouds around AGN,... The instrument is basically a two-aperture (D=40 cm) interferometer composed of three satellites, two siderostats and one beam-combiner. The formation is linear and orbits around L2, pointing in the anti-solar direction within a +/-30° cone. The baseline is adjustable from 50 to 500 m in both nulling and visibility measurement modes. The angular resolution ranges from 1 to 20 mas and the spectral resolution is 60. In the nulling mode, a 2.5 nm rms stability of the optical path difference (OPD) and a pointing stability of 30 mas rms impose a two level control architecture. It combines control loops implemented at satellite level and control loops operating inside the payload using fine mechanisms. According to our preliminary study, this mission is feasible within an 8 to 9 years development plan using existing or slightly improved space components, but its cost requires international cooperation. Pegase could be a valuable Darwin/TPF-I pathfinder, with a less demanding, but still ambitious, technological challenge and a high associated scientific return.

The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for an imaging and nulling interferometer in the near to mid-infrared spectral region (3-8 microns), and will be a scientific and technological pathfinder for upcoming missions including TPF-I/DARWIN, SPECS, and SPIRIT. At NASA's Goddard Space Flight Center, we have constructed a symmetric Mach-Zehnder nulling testbed to demonstrate techniques and algorithms that can be used to establish and maintain the 10⁴ null depth that will be required for such a mission. Among the challenges inherent in such a system is the ability to acquire and track the null fringe to the desired depth for timescales on the order of hours in a laboratory environment. In addition, it is desirable to achieve this stability without using conventional dithering techniques. We describe recent testbed metrology and control system developments necessary to achieve these goals and present our preliminary results.

Darwin is a mission under study by the European Space Agency, ESA. The mission objectives are detection and characterization of exo-planets, with special emphasize on the planets likely to harbour earthlike life. The mission cancels the light from the target star by nulling interferometry, while the light collected from any orbiting planets will interfere constructively. In this way absorption features in the planetary light can be detected and analysed. In the preceding years ESA has developed the required technology and elaborated on and evaluated different mission concepts with the aim of reducing over-all mission cost. This has resulted in a number of mission architectures, and various interferometric beam recombination techniques. To consolidate the study results two parallel mission assessment studies were initiated September 2005, taking benefit from the large number of technology developments as conducted since 2000. This article reviews the Darwin mission and its architecture evolution from the feasibility study up to the currently ongoing system assessment studies.

The proposed design includes 3 new ideas to increase the signal-noise ratio of instruments for the detection and study of extra-solar planets in space and on the ground. The instrument is to be added to systems that cancel the stellar halo, for example coronagraphs with adaptive speckle cancellation using integral field low resolution spectroscopy for speckle detection. The new design then gives an additional sensitivity to other hallo cancellation methods by hardware and/or software. The first part of the instrument spectrally splits the image into 50 to 100 narrowband images with independent optimal bandwidths and central wavelengths. This permits to have for example a uniform spectral resolution by making each bandwidth proportional to the wavelength or to adjust some bandwidths and central wavelengths to specifically target important lines. It also gives in each narrowband image optimum independent spatial sampling, for example 2 pixel per diffraction limit. This cannot be done with field sampling integral field systems as image slicers and TIGER type lens arrays. Another advantage is that there is very little contamination between spectral pixels as opposed to a slit spectrograph where the slit has a significant width compared to the pixel size, being in fact usually larger. Consequently, if a TIGER type lens array is added at the input, all 3 dimensions of the 3-D data box have very little contamination. In the second part of the instrument, the darker regions around the speckles of the narrowband images are reflected back into the spectrograph to reconstruct a white light image with a far higher contrast than at the input. The total additional gain should be equivalent to at least an order of magnitude increase in throughput. Finally, instead of reconstructing one white light image, a small number of images each with its own carefully chosen bandwidth and central wavelength can be reconstructed for specific programs as detection of life. Groups of bandwidths can also be reconstructed into white light in individual images. The system can be used as much in space than on the ground.

Precise testbeds are required to investigate the physics and engineering aspects of suppressing extrasolar starlight sufficiently to discern faint companion planets. In addition, testbeds that can simultaneously produce star and planet stimuli will be necessary ground support equipment for evaluating instruments designed for imaging and characterizing extrasolar planets. Integral to this is the ability to represent the broad spectral bands and relative geometry of stars and planets. We have built upon the Terrestrial Planet Finder Coronagraph (TPF-C) requirements as well as those of programs like Extrasolar Planet Imaging Coronagraph (EPIC) and Eclipse to develop a star/planet simulator (SPS) that, in conjunction with other testbed modules, can facilitate the pursuit of pertinent questions. The star/planet simulator developed has a broadband visible light source that illuminates independently adjustable star and planet sources (angular separation and orientation, relative magnitude). It is capable of providing either collimated or direct imaged light to proposed instruments and can be configured to produce the source stimuli in a vacuum environment. We