Over the past few years, we have developed a concept for an evolvable space telescope (EST) that is assembled on orbit in three stages, growing from a 4×12-m telescope in Stage 1, to a 12-m filled aperture in Stage 2, and then to a 20-m filled aperture in Stage 3. Stage 1 is launched as a fully functional telescope and begins gathering science data immediately after checkout on orbit. This observatory is then periodically augmented in space with additional mirror segments, structures, and newer instruments to evolve the telescope over the years to a 20-m space telescope. We discuss the EST architecture, the motivation for this approach, and the benefits it provides over current approaches to building and maintaining large space observatories.
In 2014 we presented a concept for an Evolvable Space Telescope (EST) that was assembled on orbit in 3 stages, growing from a 4x12 meter telescope in Stage 1, to a 12-meter filled aperture in Stage 2, and then to a 20-meter filled aperture in Stage 3. Stage 1 is launched as a fully functional telescope and begins gathering science data immediately after checkout on orbit. This observatory is then periodically augmented in space with additional mirror segments, structures, and newer instruments to evolve the telescope over the years to a 20-meter space telescope. In this 2015 update of EST we focus upon three items: 1) a restructured Stage 1 EST with three mirror segments forming an off-axis telescope (half a 12-meter filled aperture); 2) more details on the value and architecture of the prime focus instrument accommodation; and 3) a more in depth discussion of the essential in-space infrastructure, early ground testing and a concept for an International Space Station testbed called MoDEST. In addition to the EST discussions we introduce a different alternative telescope architecture: a Rotating Synthetic Aperture (RSA). This is a rectangular primary mirror that can be rotated to fill the UV-plane. The original concept was developed by Raytheon Space and Airborne Systems for non-astronomical applications. In collaboration with Raytheon we have begun to explore the RSA approach as an astronomical space telescope and have initiated studies of science and cost performance.
KEYWORDS: Space telescopes, Telescopes, James Webb Space Telescope, Observatories, Astrophysics, Astronomy, Space operations, Mirrors, Optical instrument design, Aerospace engineering
Astronomical flagship missions after JWST will require affordable space telescopes and science instruments. Innovative spacecraft-electro-opto-mechanical system architectures matched to the science requirements are needed for observations for exoplanet characterization, cosmology, dark energy, galactic evolution formation of stars and planets, and many other research areas. The needs and requirements to perform this science will continue to drive us toward larger and larger apertures. Recent technology developments in precision station keeping of spacecraft, interplanetary transfer orbits, wavefront/sensing and control, laser engineering, macroscopic application of nano-technology, lossless optical designs, deployed structures, thermal management, interferometry, detectors and signal processing enable innovative telescope/system architectures with break-through performance. Unfortunately, NASA’s budget for Astrophysics is unlikely to be able to support the funding required for the 8 m to 16 m telescopes that have been studied as a follow-on to JWST using similar development/assembly approaches without decimating the rest of the Astrophysics Division’s budget. Consequently, we have been examining the feasibility of developing an “Evolvable Space Telescope” that would begin as a 3 to 4 m telescope when placed on orbit and then periodically be augmented with additional mirror segments, structures, and newer instruments to evolve the telescope and achieve the performance of a 16 m or larger space telescope. This paper reviews the approach for such a mission and identifies and discusses candidate architectures.
The New Worlds Observer enables high-contrast imaging by placing a space telescope in the dark shadow cast by an
apodized starshade. This starshade is fully opaque and its performance is determined by the precise shape of the petal-like
structure. In this paper, we describe our preliminary efforts to determine the tolerance of the starshade performance
to errors in this shape.
The New Worlds Observer is a flagship-scale terrestrial planet finding and characterizing mission using an external
occulter known as a starshade. The starshade is a separate space vehicle from the observing telescope; the starshade
performs all the necessary starlight suppression to enable high contrast imaging of terrestrial exo-planets. While effective
as a flagship-scale mission designed to fulfill and exceed the requirements of the Terrestrial Planet Finder (TPF) mission,
the starshade architecture is flexible and can accommodate a variety of design and cost categories, including working
with an existing telescope. We present in this paper an architecture using a starshade with the James Web Space
Telescope (JWST), a mission concept we call New Worlds Probe, which can deliver many of the TPF mission
requirements for significantly lower mission cost. We give an overview of the science capabilities, the starshade design
and technical maturity, and concepts for starshade-JWST cooperative operation.
KEYWORDS: Space telescopes, Telescopes, Mirrors, Control systems, James Webb Space Telescope, Active vibration control, Sensors, Wavefront sensors, Actuators, Vibration control
The next generation of large space telescopes, including ATLAST, SAFIR, IXO and Generation-X will require the
development of key technologies to enable their development at an affordable cost. This includes technologies for the
rapid, low cost fabrication of ultra-light weight primary mirror segments, active figure control of primary mirror
segments, high speed wavefront sensing and control, highly-packageable and scalable deployment techniques, and active
vibration and thermal control for light weight structural elements to supply good pointing stability. In this paper we
discuss the current state-of-the-art for these technologies and roadmaps for future development in these areas.
Over the last two years, we have studied system concepts for the International X-ray Observatory (IXO) with the goal of
increasing the science return of the mission and to reduce technical and cost risk. We have developed an optical bench
concept that has the potential to increase the focal length from 20 to 25 m within the current mass and stability
requirements. Our deployable bench is a tensegrity structure formed by two telescoping booms (compression) and a
hexapod cable (tension) truss. This arrangement achieves the required stiffness for the optical bench at minimal mass
while employing only high TRL components and flight proven elements. The concept is based on existing elements, can
be fully tested on the ground and does not require new technology.
Our design further features hinged, articulating solar panels, an optical bench fully enclosed in MLI and an instrument
module with radially facing radiator panels. We find that our design can be used over a wide range of sun angles, thereby
greatly increasing IXO's field of regard, without distorting the optical bench. This makes a much larger fraction of the
sky instantaneously accessible to IXO.
The International X-ray Observatory (IXO) is a collaborative effort between NASA, ESA, and JAXA. The IXO science
goals are heavily based on obtaining high quality X-ray spectra. In order to achieve this goal the science payload will
incorporate an array of gratings for high resolution, high throughput spectroscopy at the lowest X-ray energies, 0.3 - 1.0
keV. The spectrometer will address a number of important astrophysical goals such as studying the dynamics of clusters
of galaxies, determining how elements are created in the explosions of massive stars, and revealing most of the "normal"
matter in the universe which is currently thought to be hidden in hot filaments of gas stretching between galaxies. We
present here a mature design concept for an Off-Plane X-ray Grating Spectrometer (OP-XGS). This XGS concept has
seen recent significant advancements in optical and mechanical design. We present here an analysis of how the baseline
OP-XGS design fulfills the IXO science requirements for the XGS and the optical and mechanical details of this design.
An Off-Plane X-ray Grating Spectrometer (OP-XGS) concept is being developed to meet the needs of the International
X-ray Observatory (IXO). The OP-XGS will provide the required spectral resolution of R >3000 over the 0.3 - 1 keV
band with >1000 cm2 effective collecting area, using experience gained with the current generation of reflection gratings
already flown on rocket experiments. We have developed several potential configurations that meet or exceed these
requirements. This paper will focus on the mechanical design and requirements for one of these configurations, the
"tower" concept. This configuration mounts the grating modules to the instrument platform via a tower, allowing direct
alignment with the camera module. This reduces the complexity of the alignment problem while also minimizing the
overall mass of the XGS. We have developed an initial interface concept and resource requirements for this option to be
reviewed by the mission teams for design drivers. We contrast the resource requirements for this concept with those
required for other concepts which have been reviewed by the OP-XGS team. Further, we have identified those portions
of the tower design concept that will require potential technology demonstration to reach TRL 6 prior to the Preliminary
Design Review.
A dispersive spectrometer onboard the International X-ray Observatory (IXO) provides a method for high throughput and
high spectral resolution at X-ray energies below 1 keV. An off-plane reflection grating array maximizes these
capabilities. We present here a mature mechanical design that places the grating array on the spacecraft avionics bus
13.5 m away from the focal plane. In addition, we present the technology development plan for advancing the
Technology Readiness Level to 6 for the Off-Plane X-ray Grating Spectrometer.
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 dispersive spectrometer onboard the International X-ray Observatory (IXO) provides a method for high throughput and
high spectral resolution at X-ray energies below 1 keV. An off-plane reflection grating array maximizes these
capabilities. We present here a mature mechanical design that places the grating array on the spacecraft avionics bus
13.5 m away from the focal plane.
KEYWORDS: Space telescopes, Telescopes, Planets, James Webb Space Telescope, Space operations, Stars, Interferometers, Antennas, Tolerancing, Coronagraphy
The detection and characterization of exo-solar planets, which are 25 to 30 magnitudes fainter than their (5th to 6th visual magnitude) central stars, requires large aperture telescopes that must be folded to fit within the payload fairings of existing launch vehicles, and then deployed after reaching orbit. Many other elements of the various terrestrial planet finding observatories which have been proposed also must be deployed on orbit, including sunshades, solar arrays, high gain antennas and the external occulters ("starshades") that we have been designing for a "New Worlds Observer" mission. In this paper we discuss the requirements, tolerances, design options and technology readiness levels for deployment technologies for TPF-Coronagraph, -Interferometer, and -Occulter missions and describe our strawman design concepts.
As currently envisioned, New Worlds Observer is a NASA flagship class mission, designed to fulfill the
Terrestrial Planet Finding mission objectives with a much more flexible architecture than the current TPF
design concepts. In this paper, we discuss the scalability of NWO for a variety of telescope sizes and briefly
discuss the associated science capability. In particular, the paper will address in detail three mission categories:
medium, large, and future mission concepts. Medium missions are missions with life cycle costs under $600
million dollars, including a version of NWO that may potentially fit within a MIDEX budget. Large missions
are flagship missions that involve significant science returns on a Observatory class level; this is our current
realization of NWO for the TPF mission. Future concepts use the NWO architecture, in conjunction with
enabling technologies such as in-space servicing, to solve long-term NASA missions such as Lifefinder and
Planet Imager. We present a multi-starshade NWO architecture designed for launch on an Ares V launch
vehicle as an example of a future concept.
KEYWORDS: Space telescopes, Telescopes, James Webb Space Telescope, Planets, Stars, Mirrors, Exoplanets, Visible radiation, Optical instrument design, Sun
The New Worlds Observer (NWO) mission uses a large external occulter, or "starshade," to block the light from
nearby stars and cast a deep shadow over the entrance aperture of a space telescope, enabling it to detect and characterize
Exo-Solar Planets. Since these planets are intrinsically faint (30th to 32nd magnitude), the telescope must have a large
aperture (2.4 to 4 meters) and the starshade must be large enough (25 to 50 meters) to create a shadow that is deep
enough (108 to 1010 starlight suppression) and large enough (5 to 10 meters in diameter) to envelop the telescope. The
telescope must also be far enough from the starshade (30,000 to 80,000 kilometers) that planets close to the star (50 to 65
milli-arc-seconds) are not occulted. Since the starshade's performance is inversely proportional to the wavelength of the
starlight, the telescope must operate in the visible and near infrared. The telescope should also have a significant capability
for general astrophysics observations, since it will have more than half its time available for other observations while
the starshade is moving from one target to the next.
This paper describes our conceptual design for the NWO telescope, including its instrument suite and operations concept.
We note that in addition to comparative planetology studies and the detection and characterization of terrestrial
planets, the telescope could provide a UV/Optical observing capability for the general astronomical community in the
post-HST era.
KEYWORDS: Space telescopes, James Webb Space Telescope, Telescopes, Space operations, Observatories, Space observatories, Mirrors, Sun, Far infrared, Aerospace engineering
We have developed generic mission architecture with James Webb Space Telescope heritage that can accommodate a wide variety of future space observatories. This paper describes the optimization of this architecture for the Single Aperture Far InfraRed (SAFIR) mission. This mission calls for a 10-meter telescope in an L2 orbit that is actively cooled to 4 Kelvin, enabling background-limited observations of celestial objects in the 30 to 800 micron region of the spectrum. A key feature of our architecture is a boom that attaches the payload to the spacecraft, providing thermal and dynamic isolation and minimizing disturbances from the spacecraft bus. Precision mechanisms, hinges and latches enable folding the observatory into a 5-m diameter fairing for launch and a precision deployment once on orbit. Precision mechanisms also articulate the telescope to minimize solar torques and increase the field of regard. The details of our design and the trades considered during its development are also described
KEYWORDS: Telescopes, Mirrors, Image segmentation, Space telescopes, Coronagraphy, James Webb Space Telescope, Planets, Light scattering, Off axis mirrors, Point spread functions
Use of a deployable telescope will be essential if the full science objectives of the Terrestrial Planet Finder mission are to be achieved with a visible coronagraph, since the largest monolithic mirrors that can be launched into space do not have the spatial resolution required to search the habitable zone around more than ~40 of the nearest stars. Current launch vehicle fairings limit the size of monolithic telescope mirrors to ~4 meters in diameter, or ~3.5-m x 10-m if the mirror is launched standing upright, and the telescope is unfolded after reaching orbit. By comparison, a telescope with two 3.5 x 7 meter segments could be launched and deployed autonomously to provide a 14-m elliptical aperture, and a telescope with six 4-m flat-flat hexagonal segments could be launched and deployed autonomously to provide a near-circular 12-m aperture with a single ring of segments (or 20-m if a second ring is added). Future NASA missions such as LifeFinder and planet imager will also require segmented, deployable telescopes to achieve the necessary collecting area. This paper discusses the issues associated with the use of segmented optics for coronagraphs and potential solutions.
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