This PDF file contains the front matter associated with SPIE Proceedings Volume 6958, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

The Orbital Express program was created to prove that the technical obstacles to satellite servicing were surmountable- to "take the technical excuse off the table" as it were. This mission demonstrated short range and long range autonomous rendezvous, capture and berthing, on-orbit electronics upgrades, on-orbit refueling, and autonomous fly-around visual inspection using a demonstration client satellite. The Orbital Express spacecraft were launched March 8, 2007 and completed their mission on July 22, 2007. 100% of mission success criteria and objectives were achieved. This paper describes, at a high level, the program goals and objectives, key milestones & events, accomplishments, and some of the obstacles that were overcome during the mission.

As satellite equipment and mission operations become more costly, the drive to keep working equipment running with less labor-power rises. Demonstrating the feasibility of autonomous satellite servicing was the main goal behind the Orbital Express (OE) mission. Like a tow-truck delivering gas to a car on the road, the "servicing" satellite of OE had to find the "client" from several kilometers away, connect directly to the client, and transfer fluid (or a battery) autonomously, while on earth-orbit. The mission met 100% of its success criteria, and proved that autonomous satellite servicing is now a reality for space operations. Planning the satellite mission operations for OE required the ability to create a plan which could be executed autonomously over variable conditions. As the constraints for execution could change weekly, daily, and even hourly, the tools used create the mission execution plans needed to be flexible and adaptable to many different kinds of changes. At the same time, the hard constraints of the plans needed to be maintained and satisfied. The Automated Scheduling and Planning Environment (ASPEN) tool, developed at the Jet Propulsion Laboratory, was used to create the schedule of events in each daily plan for the two satellites of the OE mission. This paper presents an introduction to the ASPEN tool, an overview of the constraints of the OE domain, the variable conditions that were presented within the mission, and the solution to operations that ASPEN provided. ASPEN has been used in several other domains, including research rovers, Deep Space Network scheduling research, and in flight operations for the NASA's Earth Observing One mission's EO1 satellite. Related work is discussed, as are the future of ASPEN and the future of autonomous satellite servicing.

The NextSat spacecraft was designed and built by Ball Aerospace & Technologies Corp. as part of the DARPA-funded Orbital Express mission. Orbital Express, launched in March of 2007, was a highly successful demonstration mission proving the feasibility of autonomous on-orbit refueling and servicing of spacecraft. The Orbital Express mission consisted of the Ball-built NextSat/CSC satellite and the Boeing-built ASTRO satellite. Both satellites launched mated into a 492km circular orbit on board a Lockheed-Martin Atlas V 401 launch vehicle from Cape Canaveral. The NextSat satellite acted as both the next generation "serviceable" satellite and the commodities satellite. This paper discusses the on-orbit mission experiences of the NextSat satellite. Key experiences include: launch and early orbit operations in which the NextSat satellite was called on to perform critical attitude control functions for the mated stack, functionality which was never tested or planned for; autonomous fluid transfers between ASTRO and NextSat; autonomous ORU transfers between ASTRO and NextSat; autonomous separation, free-flying and rendezvous operations; and end-of-life operations.

Propellant resupply of orbiting spacecraft is no longer in the realm of high risk development. The recently concluded Orbital Express (OE) mission included a fluid transfer demonstration that operated the hardware and control logic in space, bringing the Technology Readiness Level to a solid TRL 7 (demonstration of a system prototype in an operational environment). Orbital Express (funded by the Defense Advanced Research Projects Agency, DARPA) was launched aboard an Atlas-V rocket on March 9th, 2007. The mission had the objective of demonstrating technologies needed for routine servicing of spacecraft, namely autonomous rendezvous and docking, propellant resupply, and orbital replacement unit transfer. The demonstration system used two spacecraft. A servicing vehicle (ASTRO) performed multiple dockings with the client (NextSat) spacecraft, and performed a variety of propellant transfers in addition to exchanges of a battery and computer. The fluid transfer and propulsion system onboard ASTRO, in addition to providing the six degree-of-freedom (6 DOF) thruster system for rendezvous and docking, demonstrated autonomous transfer of monopropellant hydrazine to or from the NextSat spacecraft 15 times while on orbit. The fluid transfer system aboard the NextSat vehicle was designed to simulate a variety of client systems, including both blowdown pressurization and pressure regulated propulsion systems. The fluid transfer demonstrations started with a low level of autonomy, where ground controllers were allowed to review the status of the demonstration at numerous points before authorizing the next steps to be performed. The final transfers were performed at a full autonomy level where the ground authorized the start of a transfer sequence and then monitored data as the transfer proceeded. The major steps of a fluid transfer included the following: mate of the coupling, leak check of the coupling, venting of the coupling, priming of the coupling, fluid transfer, gauging of receiving tank, purging of coupling and de-mate of the coupling.

The Orbital Express Demonstration System (OEDS) flight test successfully demonstrated technologies required to autonomously service satellites on-orbit. The mission's integrated robotics solution, the Orbital Express Demonstration Manipulator System (OEDMS) developed by MDA, performed critical flight test operations. The OEDMS comprised a six-jointed robotic manipulator arm and its avionics, non-proprietary servicing and ORU (Orbital Replacement Unit) interfaces, a vision and arm control system for autonomous satellite capture, and a suite of Ground Segment and Flight Segment software allowing script generation and execution under supervised or full autonomy. The arm was mounted on ASTRO, the servicer spacecraft developed by Boeing. The NextSat, developed by Ball Aerospace, served as the client satellite. The OEDMS demonstrated two key goals of the OEDS flight test: autonomous free-flyer capture and berthing of a client satellite, and autonomous transfer of ORUs from servicer to client and back. The paper provides a description of the OEDMS and the key operations it performed.

The Orbital Express flight demonstration was established by the Defense Advanced Research Projects Agency (DARPA) to develop and validate key technologies required for cost-effective servicing of next-generation satellites. A contractor team led by Boeing Advanced Network and Space Systems built two mated spacecraft launched atop an Atlas V rocket from Cape Canaveral, Florida, on March 8, 2007. The low earth orbit test flight demonstrated on orbit transfer of hydrazine propellant, transfer of a spare battery between spacecraft and the ability to replace a spacecraft computer on orbit. It also demonstrated autonomous rendezvous and capture (AR&C) using advanced sensor, guidance, and relative navigation hardware and software. This paper summarizes the results of the on-orbit performance testing of the ARCSS (Autonomous Rendezvous and Capture Sensor System). ARCSS uses onboard visible, infrared and laser rangefinder sensors to provide real time data and imagery to the onboard sensor computer. The Boeing-developed Vis-STAR software executing on the sensor computer uses the ARCSS data to provide precision real-time client bearing, range and attitude as needed, from long range to soft capture. The paper summarizes the ARCSS and Vis-STAR on orbit performance.

The Orbital Express Autonomous Rendezvous and Capture Sensor System (ARCSS) ALONG WITH ITS Vision-based Software for Track, Attitude and Ranging (Vis-STAR) provided relative target position and attitude measurements for guidance and relative navigation during autonomous vehicle proximity operations. The use of computer and physical models during simulation, ground testing and verification of ARCSS imaging camera and software performance prior to and during on-orbit operations is discussed.

The Orbital Express ASTRO spacecraft carried multiple independent sensor systems for estimating relative state in autonomous vehicle proximity operations. The on-orbit performance of pose-estimation imaging and dedicated-target navigation solution methods are compared, for ranges between 150 meters and spacecraft capture. Variations between performance expectations from pre-flight ground tests and actual on-orbit performance are discussed. Analysis results indicate the sources of solution variations.

The Orbital Express Capture System (OECS) is one of the key technologies successfully demonstrated as part of the Orbital Express Demonstration System flight operations that took place between March and July, 2007. The OECS supported all demate, capture and berthing activities throughout the span of on-orbit activities, with no anomalies. This paper will briefly review the Orbital Express (OE) program, including goals, key milestones & events and other major subsystems particularly relevant to the OECS performance. A summary of the major activities in the Virtual System Integration process, as applied to the OECS, to ultimately verify satisfactory pre-flight performance, will be presented. Finally, actual on-orbit performance of the OECS will be described.

Measurement of the jettisoned object departure trajectory and velocity vector in the International Space Station (ISS) reference frame is vitally important for prompt evaluation of the object's imminent orbit. We report on the first successful application of photogrammetric analysis of the ISS imagery for the prompt computation of the jettisoned object's position and velocity vectors. As post-EVA analyses examples, we present the Floating Potential Probe (FPP) and the Russian "Orlan" Space Suit jettisons, as well as the near-real-time (provided in several hours after the separation) computations of the Video Stanchion Support Assembly Flight Support Assembly (VSSA-FSA) and Early Ammonia Servicer (EAS) jettisons during the US astronauts space-walk. Standard close-range photogrammetry analysis was used during this EVA to analyze two on-board camera image sequences down-linked from the ISS. In this approach the ISS camera orientations were computed from known coordinates of several reference points on the ISS hardware. Then the position of the jettisoned object for each time-frame was computed from its image in each frame of the video-clips. In another, "quick-look" approach used in near-real time, orientation of the cameras was computed from their position (from the ISS CAD model) and operational data (pan and tilt) then location of the jettisoned object was calculated only for several frames of the two synchronized movies.

The ULTOR® Passive Pose and Position Engine (P3E) technology, developed by Advanced Optical Systems, Inc (AOS), uses real-time image correlation to provide relative position and pose data for spacecraft guidance, navigation, and control. Potential data sources include a wide variety of sensors, including visible and infrared cameras. ULTOR® P3E has been demonstrated on a number of host processing platforms. NASA is integrating ULTOR® P3E into its Relative Navigation System (RNS), which is being developed for the upcoming Hubble Space Telescope (HST) Servicing Mission 4 (SM4). During SM4 ULTOR® P3E will perform realtime pose and position measurements during both the approach and departure phases of the mission. This paper describes the RNS implementation of ULTOR® P3E, and presents results from NASA's hardware-in-the-loop simulation testing against the HST mockup.

Synthetic Aperture Radar (SAR) systems typically generate copious amounts of data in the form of complex values difficult to compress. Processing this data provides real-valued images that are easier to compress, however comprehensive processing capabilities are required. Optical processor architectures provide inherent parallel computing capabilities that could be used advantageously for SAR data processing. Onboard SAR image generation would provide local access to processed information paving the way for real-time decisions. This could also provide benefits to navigation strategy or automatic instruments orientation. Moreover, for interplanetary missions or unmanned aerial vehicles (UAVs), onboard analysis of images could provide important feature identification clues and could help select the appropriate images to be transmitted to the ground (Earth). This would reduce the data throughput requirements and the related transmission bandwidth. This paper reviews the preliminary work performed for the analysis of SAR image generation using an optical processor and describes the set-up of an optical SAR processor prototype. Results of optical reconstruction of SAR signals acquired with a state-of-the-art SAR satellite are presented. Real-time processing capabilities and dynamic range calculations for a tracking optical processor architecture are also discussed.

Sparse-aperture (SA) telescopes are a technology of interest in the field of remote sensing. Significant optical resolution can be achieved by an array of sub-apertures, mitigating size and weight limitations of full aperture space-deployed sensors. Much of the analysis to date has been done with the assumption that an extended scene is spectrally flat and each pixel has the same spectrum (gray-world assumption). Previous work has found the gray-world assumption is not valid when imaging a spectrally diverse scene and/or when the optical configuration is heavily aberrated. Broadband phase diversity (BPD) is an image-based method to detect the aberrations of a system. It also assumes a gray-world. Digital simulations that quantify the limitations of BPD with respect to spectral diversity of the extended scene, the RMS of the optical path difference (OPD), noise of the system, and band width of the sensor are presented.

This paper describes the successful development and test of a multipoint fiber optic hydrogen microsensors system during the static firing of an Evolved Expandable Launch Vehicle (EELV)/Delta's common booster core (CBC) rocket engine at NASA's Stennis Space Center. The hydrogen sensitive chemistry is fully reversible and has demonstrated a response to hydrogen gas in the range of 0% to 10% with a resolution of 0.1% and a response time of ≤5 seconds measured at a gas flow rate of 1 cc/min. The system consisted of a reversible chemical interaction causing a change in reflective of a thin film of coated Palladium. The sensor using a passive element consisting of chemically reactive microcoatings deposited on the surface of a glass microlens, which is then bonded to an optical fiber. The system uses a multiplexing technique with a fiber optic driver-receiver consisting of a modulated LED source that is launched into the sensor, and photodiode detector that synchronously measures the reflected signal. The system incorporates a microprocessor to perform the data analysis and storage, as well as trending and set alarm function. The paper illustrates the sensor design and performance data under field deployment conditions.

The potential for buildup of formaldehyde in closed space environments poses a direct health hazard to personnel. The National Aeronautic Space Agency (NASA) has established a maximum permitted concentration of 0.04 ppm for 7 to 180 days for all space craft. Early detection is critical to ensure that formaldehyde levels do not accumulate above these limits. New sensor technologies are needed to enable real time, in situ detection in a compact and reusable form factor. Addressing this need, research into the use of reactive fluorescent dyes which reversibly bind to formaldehyde (liquid or gas) has been conducted to support the development of a formaldehyde sensor. In the presence of formaldehyde the dyes' characteristic fluorescence peaks shift providing the basis for an optical detection. Dye responses to formaldehyde exposure were characterized; demonstrating the optical detection of formaldehyde in under 10 seconds and down to concentrations of 0.5 ppm. To incorporate the dye in an optical sensor device requires a means of containing and manipulating the dye. Multiple form factors using two dissimilar substrates were considered to determine a suitable configuration. A prototype sensor was demonstrated and considerations for a fieldable sensor were presented. This research provides a necessary first step toward the development of a compact, reusable, real time optical formaldehyde sensor suitable for use in the U.S. space program.

Advances in aerospace applications have created a demand for the development of higher precision, higher accuracy, radiation-hardened encoders. MicroE Systems' Mercury II aerospace encoder design provides the precision and accuracy required by these applications while also addressing radiation, weight, and alignment concerns. The encoder is a grating-based, reflective, interferometric encoder consisting of three major components: a scale, a readhead, and processing electronics. The system is a kit design that is easily configured and allows for forgiving of misalignments. Its large tolerance of tilts and translations during setup and operation, make this design ideal for aerospace requirements. The system is small in footprint and weight and requires minimal power for operation. The ability to attach multiple readheads to one processing electronics unit, as well as its alignment tolerances, makes it versatile enough to meet the most demanding applications.

The European Space Agency (ESA) has committed to a multi-spacecraft Cornerstone mission to the planet Mercury. BepiColombo comprises two spacecraft, one of which (The Mercury Planetary Orbiter platform (MPO)) will contain remote sensing instruments for making measurements of the planet at wavelengths from the far infrared to γ-rays. The MERcury Thermal Infrared Spectrometer (MERTIS) measures spectral emittance from Mercury in the range from 7 to 14 μm to derive surface mineralogy. It will employ an uncooled IR focal plane array (IRFPA) at the heart of the spectrometer. Within this framework, the IRFPA has been developed from a 160 × 120 microbolometer array with a pixel pitch of 35 μm. This sensor is made from amorphous silicon, which yields a short thermal time constant as well as very low NETD. Specific attention has been paid to the fact that such detector has to operate in space environment. The paper will present the specific development under progress and the first results obtained to fulfil the MERTIS requirements in terms of performance, irradiative and mechanical environments.

An application-specific uniform calibration source is described. The biggest challenge in developing the system is to achieve 25% higher spectral radiance values than the Earth's spectral radiance, with the lowest wavelength being the hardest to meet. This pre-flight test equipment will be used for characterization and calibration of imaging radiometers which will be used as satellite-borne remote sensors for KOPMSAT-3. The integrating sphere-based system will be used as a spectral radiance standard. Included are the end user's requirements in regards to spectral radiance levels, radiance stability, radiance uniformity and spectral radiance monitoring. Detailed design challenges, approach and modeling information is discussed.

Hydra® is a modular autonomous rendezvous and docking (AR&D) sensor system for use on orbit. It uses multiple sensor heads that feed data to a single processing module, allowing the system to be configured according to mission needs. The modularity also decreases the required amount of external real estate, since the processing electronics can be internal to spacecraft. Advanced Optical Systems has built an initial Hydra® prototype that includes an Advanced Video Guidance Sensor (AVGS) and ULTOR® sensor head. The AVGS sensor head provides laser-based active measurement of distance and orientation, while the ULTOR® sensor head provides passive measurement of the same. We have tested the Hydra® prototype in the Marshall Space Flight Center's Flight Robotics Laboratory. In this paper we describe the Hydra® prototype and present the results of ground testing the sensor system.

The Rendezvous Lidar System (RLS), a high-performance scanning time-of-flight lidar jointly developed by MDA and Optech, was employed successfully during the XSS-11 spacecraft's 23-month mission. Ongoing development of the RLS mission software has resulted in an integrated pose functionality suited to safety-critical applications, specifically the terminal rendezvous of a visiting vehicle with the International Space Station (ISS). This integrated pose capability extends the contribution of the lidar from long-range acquisition and tracking for terminal rendezvous through to final alignment for docking or berthing. Innovative aspects of the technology that were developed include: 1) efficacious algorithms to detect, recognize, and compute the pose of a client spacecraft from a single scan using an intelligent search of candidate solutions, 2) automatic scene evaluation and feature selection algorithms and software that assist mission planners in specifying accurate and robust scan scheduling, and 3) optimal pose tracking functionality using knowledge of the relative spacecraft states. The development process incorporated the concept of sensor system bandwidth to address the sometimes unclear or misleading specifications of update rate and measurement delay often cited for rendezvous sensors. Because relative navigation sensors provide the measured feedback to the spacecraft GN&C, we propose a new method of specifying the performance of these sensors to better enable a full assessment of a given sensor in the closed-loop control for any given vehicle. This approach, and the tools and methods enabling it, permitted a rapid and rigorous development and verification of the pose tracking functionality. The complete system was then integrated and demonstrated in the MDA space vision facility using the flight-representative engineering model RLS lidar sensor.

For many years, many microsatellites (satellites in the 10-100 kg mass range) and nanosatellites (in the 1-10 kg mass range) missions have been designed, built and launched having the objective of technology demonstration. Recently, due to the advance of technologies over the past decade, a new trend is to use them in more demanding space missions such as space science, earth observation, flying formation and space surveillance. In micro/nano satellites applications, the need for size, mass, power consumption and cost reduction is critical. This is why there is an effort toward the development of specialized and integrated hardware. Among space hardware for satellites, the development of optical imaging payload and miniaturized attitude sensors are of great interest for space surveillance and space science applications. We proposed the development of a panomorph lens optical module designed to record wide and broadband images of a panoramic scene around the satellite. A key requirement of the optical module is therefore to be able to manage the field coverage properties to distinguish true element that can be used for star tracking, earth horizon sensing and related tracking functionalities. The optical module must provide all usable telemetric information for the satellite. The proposed technology consists of a concept of space telemetric imaging system, which will combine optically imaging for surveillance/visual monitoring of space and attitude determination capabilities in one compact and low-power consumption device for micro/nano satellite applications.