Raymond M. Bell

Updated status and capabilities for the LOTIS 6.5 meter collimator

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 Arizonas 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.

Dynamic stability with the disturbance-free payload architecture as applied to the Large UV/Optical/Infrared (LUVOIR) mission

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.

LOTIS at completion of Collimator integration

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.

Remote sensing satellite constellation for world-wide wild fire monitoring

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.

Preliminary jitter stability results for the large UV/optical/infrared (LUVOIR) surveyor concept using a non-contact vibration isolation and precision pointing system

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.

Telescope line-of-sight slew control and agility with non-contact vibration isolation for the large ultraviolet/optical/infrared (LUVOIR) surveyor concept

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.

Architecting next 30 years of climate monitoring from space with instructive examples from NPOESS and GCOS plus newrule-based decision tools: suggesting and promoting global collaborative paths forward (Part V)

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.

A Comparison of Optical Design Forms of Hyperspectral Instruments for Remote Sensing

We describe and compare five popular optical designs for remote-sensing hyperspectral sensors. We discuss the benefits and limitations of each, and consider first-order parameters that may lead a designer towards a particular option.

LOTIS facility initial operational capabilities: flexible user interfaces

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.

Triana II: a new constellation of operational earth remote sensing satellites

Understanding the earths 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.