Our recently completed study for the Advanced Technology Large-Aperture Space Telescope (ATLAST) was the culmination of three years of initially internally funded work that built upon earlier engineering designs, science objectives, and technology priorities. Beginning in the mid-1980s, multiple teams of astronomers, technologists, and engineers developed concepts for a large-aperture UV/optical/IR space observatory intended to follow the Hubble Space Telescope (HST). Here, we summarize since the first significant conferences on major post-HST ultraviolet, optical, and infrared (UVOIR) observatories the history of designs, scientific goals, key technology recommendations, and community workshops. Although the sophistication of science goals and the engineering designs both advanced over the past three decades, we note the remarkable constancy of major characteristics of large post-HST UVOIR concepts. As it has been a priority goal for NASA and science communities for a half-century, and has driven much of the technology priorities for major space observatories, we include the long history of concepts for searching for Earth-like worlds. We conclude with a capsule summary of our ATLAST reference designs developed by four partnering institutions over the past three years, which was initiated in 2013 to prepare for the 2020 National Academies’ Decadal Survey.
The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8- to 16-m ultraviolet optical near infrared space observatory for launch in the 2025 to 2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including: Is there life elsewhere in the Galaxy? We present a range of science drivers and the resulting performance requirements for ATLAST (8- to 16-marcsec angular resolution, diffraction limited imaging at 0.5-μm wavelength, minimum collecting area of 45 m2, high sensitivity to light wavelengths from 0.1 to 2.4 μm, high stability in wavefront sensing and control). We also discuss the priorities for technology development needed to enable the construction of ATLAST for a cost that is comparable to that of current generation observatory-class space missions.
The Advanced Technology for Large Aperture Space Telescope (ATLAST) concept was assessed as one of the NASA
Astrophysics Strategic Mission Concepts (ASMC) studies. Herein we discuss the 9.2-meter diameter segmented aperture
version and its wavefront sensing and control (WFSC) with regards to coronagraphic detection and spectroscopic
characterization of exoplanets. The WFSC would consist of at least two levels of sensing and control: (i) an outer coarser
level of sensing and control to phase and control the segments and secondary mirror in a manner similar to the James
Webb Space Telescope but operating at higher temporal bandwidth, and (ii) an inner, coronagraphic instrument based,
fine level of sensing and control for both amplitude and wavefront errors operating at higher temporal bandwidths. The
outer loop would control rigid-body actuators on the primary and secondary mirrors while the inner loop would control
one or more segmented deformable mirror to suppress the starlight within the coronagraphic field-of-view. Herein we
discuss the visible nulling coronagraph (VNC) and the requirements it levies on wavefront sensing and control and show
the results of closed-loop simulations to assess performance and evaluate the trade space of system level stability versus
We present results of a study of a deployable version of the Advanced Technology Large-Aperture Space Telescope
(ATLAST), designed to operate in a Sun-Earth L2 orbit. The primary mirror of the segmented 9.2-meter aperture has 36
hexagonal 1.315 m (flat-to-flat) glass mirrors. The architecture and folding of the telescope is similar to JWST, allowing
it to fit into the 6.5 m fairing of a modest upgrade to the Delta-IV Heavy version of the Evolved Expendable Launch
Vehicle (EELV). We discuss the overall observatory design, optical design, instruments, stray light, wavefront sensing
and control, pointing and thermal control, and in-space servicing options.
Following recommendations by the NRC, NASA's FY 2008 Authorization Act and the
FY 2009 and 2010 Appropriations bills directed NASA to assess the use of the human
spaceflight architecture to service existing/future observatory-class scientific spacecraft.
This interest in satellite servicing, with astronauts and/or with robots, reflects the success
that NASA achieved with the Shuttle program and HST on behalf of the astronomical
community as well as the successful construction of ISS. This study, led by NASA
GSFC, will last about a year, leading to a final report to NASA and Congress in autumn
2010. We will report on its status, results from our March satellite servicing workshop,
and recent concepts for serviceable scientific missions.
The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR
space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at
the forefront of modern astronphysics, including "Is there life elsewhere in the Galaxy?" We present a range of science
drivers that define the main performance requirements for ATLAST (8 to 16 milliarcsec angular resolution, diffraction
limited imaging at 0.5 μm wavelength, minimum collecting area of 45 square meters, high sensitivity to light
wavelengths from 0.1 μm to 2.4 μm, high stability in wavefront sensing and control). We will also discuss the synergy
between ATLAST and other anticipated future facilities (e.g., TMT, EELT, ALMA) and the priorities for technology
development that will enable the construction for a cost that is comparable to current generation observatory-class space
Future large UV-optical space telescopes offer new and exciting windows of scientific parameter space. These
telescopes can be placed at L2 and borrow heavily from the James Webb Space Telescope (JWST) heritage. For
example, they can have similar deployment schemes, hexagonal mirrors, and use Wavefront Sensing and Control
(WFSC) technologies developed for JWST. However, a UV-optical telescope requires a 4x improvement in
wavefront quality over JWST to be diffraction-limited at 500 nm. Achieving this tolerance would be difficult using
a passive thermal architecture such as the one employed on JWST. To solve this problem, our team has developed a
novel Hybrid Sensor Active Control (HSAC) architecture that provides a cost effective approach to building a
segmented UV-optical space telescope. In this paper, we show the application of this architecture to the ST-2020
mission concept and summarize the technology development requirements.
We present the results of the Astrophysics Strategic Mission Concept Study for the New Worlds Observer (NWO). We show that the
use of starshades is the most effective and affordable path to mapping and understanding our neighboring planetary systems, to opening
the search for life outside our solar system, while serving the needs of the greater astronomy community. A starshade-based mission
can be implemented immediately with a near term program of technology demonstration.
A key component of our 2008 NASA Astrophysics Strategic Mission Concept Study entitled "An Advanced
Technology Large-Aperture Space Telescope: A Technology Roadmap for the Next Decade" is the
identification of the astrophysics that can be uniquely accomplished using a filled, large-aperture UV/optical
space telescope with an angular resolution 5 - 10 times better than JWST. We summarize here four research
areas that are amongst the prime drivers for such an advanced astronomical facility: 1) the detection of
habitability and bio-signatures on terrestrial mass exoplanets, 2) the reconstruction of the detailed history of
the assembly of stellar mass in the local universe, 3) establishing the mass function and characterizing the
accretion environments of supermassive black holes out to redshifts of z ~ 7, and 4) the precise determination
of growth of structure in the universe by kinematic mapping of the dark matter halos of galaxies as functions
of time and environment.
We present a conceptual design for a scalable (10-50 meter segmented filled-aperture) space observatory operating at UV-optical-near infrared wavelengths. This telescope is designed for assembly in space by robots, astronauts or a combination of the two, as envisioned in NASA's Vision for Space Exploration. Our operations concept for this space telescope provides for assembly and check-out in an Earth Moon L2 (EML2) orbit, and transport to a Sun-Earth L2 (SEL2) orbit for science operations and routine servicing, with return to EML2 for major servicing. We have developed and analyzed initial designs for the optical, structural, thermal and attitude control systems for a 30-m aperture space telescope. We further describe how the separate components are packaged for launch by heavy lift vehicle(s) and the approach for the robot assembly of the telescope from these components.
The Far Ultraviolet Spectroscopic Explorer satellite (FUSE)
is a NASA Origins mission launched on 1999 June 24 and
operated from the Johns Hopkins University Homewood campus in
Baltimore, MD. FUSE consists of four aligned telescopes feeding
twin far-ultraviolet spectrographs that achieve a spectral
resolution of R=20,000 over the 905-1187 Å spectral region.
This makes FUSE complementary to the Hubble Space Telescope
and of broad general interest to the astronomical community.
FUSE is operated as a general-purpose observatory with
proposals evaluated and selected by NASA.
The FUSE mission concept evolved dramatically over time. The
version of FUSE that was built and flown was born out of the
"faster, better, cheaper" era, which drove not only the
mission development but also plans for operations. Fixed price
contracts, a commercial spacecraft, and operations in the
University environment were all parts of the low cost strategy.
The satellite performs most functions autonomously, with ground
contacts limited typically to seven 12-minute contacts per
day through a dedicated ground station. All support functions
are managed by a staff of 40 scientists and engineers located at
Johns Hopkins. In this configuration, we have been able to achieve
close to 30% average on-target science efficiency. In short, FUSE is a successful example of the "faster, better, cheaper" philosophy.
The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was launched on June 24, 1999. FUSE is designed to make high resolution ((lambda) /(Delta) (lambda) equals 20,000 - 25,000) observations of solar system, galactic, and extragalactic targets in the far ultraviolet wavelength region (905 - 1187 angstrom). Its high effective area, low background and planned three year life allow observations of objects which have been too faint for previous high resolution instruments in this wavelength range. FUSE has now been in orbit for one year. We discuss the accomplishments of the FUSE mission during this time, and look ahead to the future now that normal operations are under way.
The FUSE satellite employs innovative techniques for autonomous target acquisitions and fine pointing control. One of two Fine Error Sensors, incorporated in the optical path of the science instrument, provide the Instrument Data System computer with images, for target identification, and field star centroids, for fine pointing information to the spacecraft attitude control system. A suite of 'toolbox' functions has been developed to locate stars, selected and track on 'unknown' guide stars from the image, identify the star field, track preselected 'known' guide stars, follow moving targets, and provide pointing optimizations to fine- tune the centering of a target. After a maneuver to a new field, initial attitude is determined by identifying stars found in a 20' X 20' image. Identification is done by matching stars with an uploaded table of up to 200 objects selected from the Hubble Space Telescope (HST) Guide Star Catalog (GSC), ranging from V equals 9 to 13.5 mag., and typically covering a one degree field around the target. During identification, tracking is performed on unidentified stars in the image to prevent the satellite from drifting. A corrective slew is then commanded to place the target at the desired position. Tracking is then resumed on preselected guide stars. If desired, further fine alignment of the science apertures is performed by a target peakup using the FUV detectors. We discuss the target acquisition process; end-to- end performance; and problems encountered due to the limitations of the small field of view of the FES, HST GSC errors, and stray light in the telescope baffles.
The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was launched into orbit on June 24, 1999. FUSE is now making high resolution ((lambda) /(Delta) (lambda) equals 20,000 - 25,000) observations of solar system, galactic, and extragalactic targets in the far ultraviolet wavelength region (905 - 1187 angstroms). Its high effective area, low background, and planned three year life allow observations of objects which have been too faint for previous high resolution instruments in this wavelength range. In this paper, we describe the on- orbit performance of the FUSE satellite during its first nine months of operation, including measurements of sensitivity and resolution.
This paper describes how the OPUS pipeline, currently used for processing science data from the Hubble Space Telescope (HST), was used as the backbone for developing the science data pipeline for a much smaller mission. The far ultraviolet spectroscopic explorer (FUSE) project selected OPUS for its data processing pipeline platform and selected the OPUS team at the STScI to write the FUSE pipeline applications. A total of 105 new modules were developed for the FUSE pipeline. The foundation of over 250 modules in the OPUS libraries allowed development to proceed quickly and with considerable confidence that the underlying functionality is reliable and robust. Each task represented roughly 90 percent reuse, and the project as a whole shows over 70 percent reuse of the existing OPUS system. Taking an existing system that is operational, and will be maintained for many years to come, was a key decision for the FUSE mission. Adding the extensive experience of the OPUS team to the task resulted in the development of a complete telemetry pipeline system within a matter of months. Reusable software has been the siren song of software engineering and object- oriented design for a decade or more. The development of inexpensive software systems by adapting existing code to new applications is as attractive as it has been elusive. The OPUS telemetry pipeline for the FUSE mission has proven to be a significant exception to that trend.
The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite will obtain high spectral resolving power ((lambda) /(Delta) (lambda) equals 30,000) measurements of astrophysical objects in the 905 - 1195 angstroms wavelength region from low-earth orbit. The instrument's high effective area (30 - 100 cm2) and low detector background will permit observations of solar system, galactic, and extragalactic targets that have been too faint for previous instruments at this high resolution. The instrument design achieves both high resolution and high throughput by using four nearly identical optical channels. The optics consist of four normal incidence mirrors, four high density holographically-ruled diffraction gratings, and a pair of large format double delay line detectors. These components are supported by a graphite-composite structure. A commercially-procured spacecraft provides pointing stability of 0.5 arcseconds (1 (omega) ), by using data from a Fine Error Sensor included in the instrument. In early 1995 the FUSE mission was reconstructed to be a lower-cost, PI-class mission. The construction phase began in December, 1995, and launch is scheduled for late 1998. We present a description of the FUSE instrument, including details of the optical and mechanical design, along with an estimate of its on-orbit performance.