KEYWORDS: Space telescopes, Telescopes, James Webb Space Telescope, Mirrors, Optical instrument design, Astronomy, Space operations, Cryogenics, Aerospace engineering, Cryocoolers
The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? We describe how Origins was designed to answer these alluring questions. We discuss the key decisions taken by the Origins mission concept study team, the rationale for those choices, and how they led through an exploratory design process to the Origins baseline mission concept. To understand the concept solution space, we studied two distinct mission concepts and descoped the second concept, aiming to maximize science per dollar and hit a self-imposed cost target. We report on the study approach and describe the concept evolution. The resulting baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. The chosen architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch. The cryo-thermal system design leverages James Webb Space Telescope technology and experience.
The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the Universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared (IR) wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of the Herschel Space Observatory, the largest telescope flown in space to date. We describe the baseline concept for Origins recommended to the 2020 US Decadal Survey in Astronomy and Astrophysics. The baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (Mid-Infrared Spectrometer and Camera Transit spectrometer) will measure the spectra of transiting exoplanets in the 2.8 to 20 μm wavelength range and offer unprecedented spectrophotometric precision, enabling definitive exoplanet biosignature detections. The far-IR imager polarimeter will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer will cover wavelengths from 25 to 588 μm, making wide-area and deep spectroscopic surveys with spectral resolving power R ∼ 300, and pointed observations at R ∼ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch, while the cryothermal system design leverages James Webb Space Telescope technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural background-limited sensitivity.
The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of Herschel, the largest telescope flown in space to date. After a 3 ½ year study, the Origins Science and Technology Definition Team will recommend to the Decadal Survey a concept for Origins with a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (MISC-T) will measure the spectra of transiting exoplanets in the 2.8 – 20 μm wavelength range and offer unprecedented sensitivity, enabling definitive biosignature detections. The Far-IR Imager Polarimeter (FIP) will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer (OSS) will cover wavelengths from 25 – 588 μm, make wide-area and deep spectroscopic surveys with spectral resolving power R ~ 300, and pointed observations at R ~ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The telescope has a Spitzer-like architecture and requires very few deployments after launch. The cryo-thermal system design leverages JWST technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural backgroundlimited sensitivity.
The Large Optical Test and Integration Site (LOTIS) Facility at Lockheed Martin Space Systems Company in Sunnyvale, CA has been design specifically to accommodate assembly, integration, and testing of optical payloads from as small as 1 meter class apertures to as large as 6 meters. The facility has successfully reached initial operational capability and a basic overview of the LOTIS Facility has been previously reported including wavefront performance [1], its potential for optical payload testing has been previously reported [2]. The facility has been engineered from the foundation up to provide an ideal single location for optical payloads including details such as crane access, clean room space and levels, vibration levels, and atmospheric turbulence levels within the facility especially the interior of the vacuum chamber containing the 6.5 meter collimator. This paper will present and overview of the facility in general and then present results of the vibration isolation bench performance and resulting line of sight jitter of the collimator, as well as atmospheric turbulence measurements within the chamber.
The Origins Space Telescope (OST) will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.
KEYWORDS: Mirrors, Space operations, Control systems, Interfaces, Space telescopes, Finite element methods, Performance modeling, Wavefronts, Telescopes, Error analysis
The need for high payload dynamic stability and ultra-stable mechanical systems is an overarching technology need for large space telescopes such as the Large Ultraviolet / Optical / Infrared (LUVOIR) Surveyor concept. The LUVOIR concept includes a 15-meter-diameter segmented-aperture telescope with a suite of serviceable instruments operating over a range of wavelengths between 100 nm to 2.5 μm. Wavefront error (WFE) stability of less than 10 picometers RMS of uncorrected system WFE per wavefront control step represents a drastic performance improvement over current space-based telescopes being fielded. Through the utilization of an isolation architecture that involves no mechanical contact between the telescope and the host spacecraft structure, a system design is realized that maximizes the telescope dynamic stability performance without driving stringent technology requirements on spacecraft structure, sensors or actuators. Through analysis of the LUVOIR finite element model and linear optical model, the wavefront error and Line- Of-Sight (LOS) jitter performance is discussed in this paper when using the Vibration Isolation and Precision Pointing System (VIPPS) being developed cooperatively with Lockheed Martin in addition to a multi-loop control architecture. The multi-loop control architecture consists of the spacecraft Attitude Control System (ACS), VIPPS, and a Fast Steering Mirror on the instrument. While the baseline attitude control device for LUVOIR is a set of Control Moment Gyroscopes (CMGs), Reaction Wheel Assembly (RWA) disturbance contribution to wavefront error stability and LOS stability are presented to give preliminary results in this paper. CMG disturbance will be explored in further work to be completed.
The Large Ultraviolet / Optical / Infrared (LUVOIR) mission concept intends to determine not only if habitable exoplanets exist outside our solar system, but also how common life might be throughout the galaxy. This surveying objective implies a high degree of angular agility of a large segmented optical telescope, whose performance requires extreme levels of dynamic stability and isolation from spacecraft disturbance. The LUVOIR concept architecture includes a non-contact Vibration Isolation and Precision Pointing System (VIPPS), which allows for complete mechanical separation and controlled force/torque exchange between the telescope and spacecraft by means of non-contact actuators. LUVOIR also includes an articulated two-axis gimbal to allow for telescope pointing while meeting sun-pointing constraints of the spacecraft-mounted sunshade. In this paper, we describe an integrated pointing control architecture that enables largeangle slewing of the telescope, while maintaining non-contact between telescope and spacecraft, in addition to meeting the LUVOIR line-of-sight agility requirement. Maintaining non-contact during slews preserves telescope isolation from spacecraft disturbances, maximizing the availability of the LUVOIR observatory immediately after repositioning maneuvers. We show, by means of a detailed multi-body nonlinear simulation with a model of the proposed control architecture, that this non-contact slew performance can be achieved within the size, weight and power capabilities of the current voice coil actuator designs for the LUVOIR mission concept.
The need for high payload dynamic stability and ultra-stable mechanical systems is an overarching technology need for large space telescopes such as the Large Ultraviolet / Optical / Infrared (LUVOIR) Surveyor. Wavefront error stability of less than 10 picometers RMS of uncorrected system WFE per wavefront control step represents a drastic performance improvement over current space-based telescopes being fielded. Previous studies of similar telescope architectures have shown that passive telescope isolation approaches are hard-pressed to meet dynamic stability requirements and usually involve complex actively-controlled elements and sophisticated metrology. To meet these challenging dynamic stability requirements, an isolation architecture that involves no mechanical contact between telescope and the host spacecraft structure has the potential of delivering this needed performance improvement. One such architecture, previously developed by Lockheed Martin called Disturbance Free Payload (DFP), is applied to and analyzed for LUVOIR. In a noncontact DFP architecture, the payload and spacecraft fly in close proximity, and interact via non-contact actuators to allow precision payload pointing and isolation from spacecraft vibration. Because disturbance isolation through non-contact, vibration isolation down to zero frequency is possible, and high-frequency structural dynamics of passive isolators are not introduced into the system. In this paper, the system-level analysis of a non-contact architecture is presented for LUVOIR, based on requirements that are directly traceable to its science objectives, including astrophysics and the direct imaging of habitable exoplanets. Aspects of architecture and how they contribute to system performance are examined and tailored to the LUVOIR architecture and concept of operation.
Collecting the earth’s critical climate signatures over the next 30 years is an obvious priority for many world
governments and international organizations. Implementing a solution requires bridging from today’s scientific
missions to ‘operational’ constellations that are adequate to support the future demands of decision makers,
scientific investigators and global users for trusted data.
Architecting the operational Next Generation of earth monitoring satellites based on matured climate modeling, reuse of existing sensor & satellite capabilities, attention to affordability and evolutionary improvements integrated with constellation efficiencies - becomes our collective goal for an open architectural design forum. Understanding the earth's climate and collecting requisite signatures over the next 30 years is a shared mandate by many of the world's governments. But there remains a daunting challenge to bridge scientific missions to 'operational' systems that truly support the demands of decision makers, scientific investigators and global users' requirements for trusted data. In this paper we will suggest an architectural structure that takes advantage of current earth modeling examples including cross-model verification and a first order set of critical climate parameters and metrics; that in turn, are matched up with existing space borne collection capabilities and sensors. The tools used and the frameworks offered are designed to allow collaborative overlays by other stakeholders nominating different critical parameters and their own treaded connections to existing international collection experience. These aggregate design suggestions will be held up to group review and prioritized as potential constellation solutions including incremental and spiral developments - including cost benefits and organizational opportunities. This Part IV effort is focused on being an inclusive 'Next Gen Constellation' design discussion and is the natural extension to earlier papers.
Understanding the earth's climate and collecting the requisite signatures over the next 10, 20, 30 years is a shared
mandate by many of the world's governments. But there remains a daunting challenge to bridge scientific missions to
'operational' systems that truly support the demands of decision makers, scientific investigators and global users'
requirements for trusted data. For this Part III paper, we will examine the required components of a coupled modeling
framework to perform, with benefit of adjoint constraints , optimal forward modeling of the climate's GHG's for both
demonstration and verification. Interrogating such forward modeling in detail will help uncover the most efficient and
sufficient set of critical climate parameters & metrics needed to systematic capture and attribute climate monitoring
environmental records. This in turn would allow globally trusted algorithms to produce climate products that the world's
governments can use to most accurately assess man's impacts on earth's climate and promote informed decisions
sustaining the earth's ability to support life. This paper is the climate modeling based extension to two earlier papers
from 2009 & 2010.
An imaging test bed has been constructed for exploring the design considerations for selecting the appropriate image
sampling or Q for electro-optical earth imaging systems where Q is defined as (λf/#) / pixel pitch. The test bed includes
errors such as image smear and shot noise produced by atmospheric haze. The value of Q can be varied by either
changing the focal length of the imaging system or by varying the imaging aperture diameter. All of these parameters are
varied to understand the effects on image quality. In this paper we explore practical design considerations for selecting Q
for an electro-optical earth imaging system. In particular we will focus on image degradation caused by increasing Q by
reducing the imaging aperture diameter.
Understanding the earth"s climate and collecting suitable signatures over the next 10, 20, 30 years is a shared objective
of many world governments. But even with significant scientific progress and demonstrations to date, there remains a
daunting challenge to bridge from scientific missions to "operational" systems that support decision makers, scientific
communities and vast numbers of users eager for verified data. In this part II paper for 2010, an expanded description of
a system of constellations reveals the capacity of supporting multiple existing missions and additional "decadal survey"
objectives, by leveraging today's capabilities in an expandable architecture. Resourcing a system of systems solution is
also challenging, but thoughts on shared cost efficiencies and common concerns will be offered specifically intended to
focus the "community" discussion on incremental solutions.
The Large Optical Test and Integration Site (LOTIS) at the Lockheed Martin Space Systems
Company in Sunnyvale, CA, has successfully reached Initial Operational Capability (IOC).
LOTIS is designed for the verification and testing of optical systems. The facility consists of a
large, temperature stabilized vacuum chamber that also functions as a class 10k cleanroom.
Within this chamber and atop an advanced vibration-isolation bench are the 6.5 meter diameter
LOTIS Collimator and Scene Generator, LOTIS alignment and support equipment. IOC included
completion of the entire facility as well as operation of the LOTIS collimator in air. Wavefront
properties of the collimator will be described as well as facility vibration isolation properties and
turbulence levels within the collimator test chamber. User-specific test capabilities will also be
addressed for two major areas of concern.
Satellite remote sensing can provide continuous surveillance to detect, characterize, and map wild fires, agricultural
fires, and land management fires. Fire management challenges require additional capability to allow rapid revisit rates,
rapid tasking, and data delivery to the field sufficient for fire management agencies in modern and developing nations
worldwide. An analysis and description of the required constellation of satellites and sensors is given with consideration
of tasking and data delivery.
Remote-sensing hyperspectral sensors operating in the reflective bands offer the opportunity to vastly improve land
management worldwide by providing continuous coverage and continuity of satellite capability. We assess the
requirements for such sensors that will provide the needed revisit rates, coverage and imaging performance. From these
requirements we select a range of potential system-level architectures, and derive their constellations, including orbital
parameters and the number of needed satellites. We further discuss how the initial requirements drive the architecture
parameters and performance. We demonstrate that a single satellite will not meet the current needs of the environmental
sensing community, rather a constellation of multiple operational satellites is required for desirable worldwide land
management missions.
Understanding the earth's climate and the how it supports life is essential to government policy makers. A new
constellation of operational earth remote sensing satellites (Triana II) is required to provide data to develop this
understanding. Comparison of several spacecraft, sensors systems, orbits, and constellations is described and one
recommended that will support many of the policy decisions facing governments around the world over the next critical
decades.
Digital Holography is a technique which provides a measurement of the complex field reflecting from a coherently
illuminated object. When the measurement is performed with two carefully chosen wavelengths a phase difference map
can be created providing a three dimensional map of the object. We present results from a laboratory experiment where
the surface contours of coral are measured in seawater. Contour maps with step sizes on the order of 0.1 mm can easily
be obtained. We propose that this technique be used to remotely monitor the growth of coral in an effort to quantify the
health of coral beds. The technique is effective from space, aircraft, ships, buoys or rigid platforms such as a pier. In the
last few years we have been successfully using this technique to measure objects through very turbulent atmosphere at
ranges of up to 700 meters and we are now applying the concept to shoreline applications.
The Large Optical Test and Integration Site (LOTIS) at Lockheed Martin Space Systems Company (LMSSC) in
Sunnyvale, California was designed and constructed in order to allow advanced optical testing for systems up to a
maximum aperture of up to 6.5 meters in air or vacuum over a bandwidth of 0.4 to over 5 μm with a design field of view
of 1.5 milliradians. Previously reported information for the LOTIS 6.5 meter diameter Collimator was based on data
collected during initial testing of this device at the University of Arizona's Steward Observatory Mirror Laboratory. This
paper will report progress and new results for the LOTIS Collimator as it is re-assembled and tested during its final
integration into its facility at LMSSC. In addition, we will discuss Scene Projection Technology (SPT) capabilities that
can be added to provide user test capabilities meeting or exceeding many of the original specifications of the Collimator,
primarily in increased optical bandwidth and field-of-view. Finally, we will describe additional optical tools (e.g.,
interferometers and smaller collimators) that are integral to the LOTIS facility that can provide flexible optical testing
options for a wide array of users.
The Large Optical Test and Integration Site (LOTIS) at the Lockheed Martin Space Systems Company in Sunnyvale,
CA is designed for the verification and testing of optical systems. The facility consists of a large, temperature
stabilized vacuum chamber that also functions as a class 10k cleanroom. Within this chamber and atop an advanced
vibration-isolation bench are the 6.5 meter diameter LOTIS Collimator and Scene Generator, LOTIS alignment and
support equipment. The optical payloads are also placed on the vibration bench in the chamber for testing. The Scene
Generator is attached to the Collimator forming the Scene Projection System (SPS) and this system is designed to
operate in both air and vacuum, providing test imagery in an adaptable suite of visible/near infrared (VNIR) and
midwave infrared (MWIR) point sources, and combined bandwidth visible-through-MWIR point sources, for testing
of large aperture optical payloads. The heart of the SPS is the LOTIS Collimator, a 6.5m f/15 telescope, which projects
scenes with wavefront errors <85 nm rms out to a ±0.75 mrad field of view (FOV). Using field lenses, performance
can be extended to a maximum field of view of ±3.2 mrad. The LOTIS Collimator incorporates an extensive integrated
wavefront sensing and control system to verify the performance of the system, and to optimize its actively controlled
primary mirror surface and overall alignment. Using these optical test assets allows both integrated component and
system level optical testing of electro-optical (EO) devices by providing realistic scene content. LOTIS is scheduled to
achieve initial operational capability in 2008.
The effects upon imaging due to varying the spatial coherence of the illumination in an optical system are studied. A rotating diffuser is located directly behind the object in an optical system and is trans-illuminated with spatially coherent monochromatic light. The statistical properties of the diffuser surface determine the scattering cone angle and the partial coherence effects in the image. A model is presented that can be used to determine the diffuser properties required to yield incoherent imaging. Two metrics are used to determine if an image is incoherent: the apparent transfer function and image contrast.
Visible interferometry at µarc-second accuracy requires measurement of the interferometric baseline length and orientation at picometer accuracy. The optical metrology instruments required for these interferometers must achieve accuracy on order of 1 to 10 picometers. This paper discusses the progress in the development of optical interferometers for use in distance measurement gauges with systematic errors below 100 picometers. The design is discussed as well as test methods and test results.
The Space Interferometer Mission (SIM) demands extremely precise and well-characterized laser metrology gauges (also called beam launchers) to monitor the internal and external optical delay quantities which are required for astrometric measurements. In general, any space-based sparse aperture system will require laser metrology gauges for high-bandwidth sensing of phasing errors. Lockheed Martin has aggressively pursued a technology development program for high-accuracy, space-qualified laser gauge systems. Part of this effort is focused on making compact, lightweight, low-power consumption, relatively inexpensive beam-launcher units using integrated-optics components. This paper will describe the design, laboratory implementation, performance, and error analysis for an integrated-optic based laser gauge that was constructed in FY 2000-2001 using commercially available heterodyne interferometer optics and electronics, combined with commercial fiber-optic cables and splitters. In order to provide for heterodyne mixing between the signals in the reference and measurement arms of the gauge, polarization-maintaining (PM) fiber components were used. The PM fiber lengths were matched to within 0.5 mm to avoid differential thermal effects in the measurement and reference arms. Steps were also taken to minimize the cyclic phase error due to polarization leakage, and the residual cyclic errors were measured. While not meeting the extreme picometer-level measurement accuracy requirements of SIM, the gauge can distinguish optical path differences to better than a 10 nm accuracy, which is sufficient for many space applications.
Closed loop wave front correction of low order Zernike polynomials has been demonstrated using a phase diversity wavefront sensor. The Lockheed-Martin Advanced Technology Center phase diversity brassboard was used to demonstrate low bandwidth correction of aberrations consisting of the Zernike polynomials describing focus, coma and spherical. The method of Lofdahl-Scharmer is used to estimate and correct fixed aberrations in an optical system. The General Regression Neural Network method is used to estimate slowly varying aberrations in the same optical system. Closed loop experimental results from these tests are presented.
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