Optical Navigation Algorithm Performance

There is a wide variety of optical navigation (OpNav) techniques that can be used to extract observables from images of natural bodies. Each of these techniques has a number of strengths and weaknesses and domains where they are most applicable. In this paper, we compare the performance of some of the most commonly used OpNav techniques across a variety of orbital regimes and a variety of body types through the use of synthetic images. Specifically, we consider the techniques of analytic model fitting, phase corrected moment estimation, limb-scanning, ellipsoid matching, and cross correlation using synthetic images of a tri-axial ellipsoid, the asteroid Bennu, and the comet 67P/Churyumov-Gerasimenko. For each technique, regime, and body, we examine the overall accuracy and the type of information available. The resulting information provides a useful tool for understanding which techniques are best suited for a given image, as well as for understanding the relative performance of each technique

Linear Covariance Analysis For Proximity Operations Around Asteroid 2008 EV5

The NASA initiative to collect an asteroid, the Asteroid Robotic Redirect Mission (ARRM), is currently investigating the option of retrieving a boulder from an asteroid, demonstrating planetary defense with an enhanced gravity tractor technique, and returning it to a lunar orbit. Techniques for accomplishing this are being investigated by the Satellite Servicing Capabilities Office (SSCO) at NASA GSFC in collaboration with JPL, NASA JSC, LaRC, and Draper Laboratory, Inc. Two critical phases of the mission are the descent to the boulder and the Enhanced Gravity Tractor demonstration. A linear covariance analysis is done for these phases to assess the feasibility of these concepts with the proposed design of the sensor and actuator suite of the Asteroid Redirect Vehicle (ARV). The sensor suite for this analysis includes a wide field of view camera, LiDAR, and an IMU. The proposed asteroid of interest is currently the C-type asteroid 2008 EV5, a carbonaceous chondrite that is of high interest to the scientific community. This paper presents an overview of the linear covariance analysis techniques and simulation tool, provides sensor and actuator models, and addresses the feasibility of descending to the surface of the asteroid within allocated requirements as well as the possibility of maintaining a halo orbit to demonstrate the Enhanced Gravity Tractor technique

Proximity Operations for the Robotic Boulder Capture Option for the Asteroid Redirect Mission

In September of 2013, the Asteroid Robotic Redirect Mission (ARRM) Option B team was formed to expand on NASA's previous work on the robotic boulder capture option. While the original Option A concept focuses on capturing an entire smaller Near-Earth Asteroid (NEA) using an inflatable bag capture mechanism, this design seeks to land on a larger NEA and retrieve a boulder off of its surface. The Option B team has developed a detailed and feasible mission concept that preserves many aspects of Option A's vehicle design while employing a fundamentally different technique for returning a significant quantity of asteroidal material to the Earth-Moon system. As part of this effort, a point of departure proximity operations concept was developed complete with a detailed timeline, as well as DeltaV and propellant allocations. Special attention was paid to the development of the approach strategy, terminal descent to the surface, controlled ascent with the captured boulder, and control during the Enhanced Gravity Tractor planetary defense demonstration. The concept of retrieving a boulder from the surface of an asteroid and demonstrating the Enhanced Gravity Tractor planetary defense technique is found to be feasible and within the proposed capabilities of the Asteroid Redirect Vehicle (ARV). While this point of departure concept initially focuses on a mission to Itokawa, the proximity operations design is also shown to be extensible to wide range of asteroids

Performance Characterization of a Landmark Measurement System for ARRM Terrain Relative Navigation

This paper describes the landmark measurement system being developed for terrain relative navigation on NASAs Asteroid Redirect Robotic Mission (ARRM),and the results of a performance characterization study given realistic navigational and model errors. The system is called Retina, and is derived from the stereophotoclinometry methods widely used on other small-body missions. The system is simulated using synthetic imagery of the asteroid surface and discussion is given on various algorithmic design choices. Unlike other missions, ARRMs Retina is the first planned autonomous use of these methods during the close-proximity and descent phase of the mission

Relative Terrain Imaging Navigation for the Asteroid Redirect Robotic Mission (ARRM)

No abstract availabl

Navigation filter design and comparison for Texas 2 STEP nanosatellite

textA Discrete Extended Kalman Filter has been designed to process measurements from a magnetometer, sun sensor, IMU, and GPS receiver to provide the relative position, velocity, attitude, and gyro bias of a chaser spacecraft relative to a target spacecraft. An Extended Kalman Filter with Uncompensated Bias has also been developed for the implementation of well known biases and errors that are not directly observable. A detailed explanation of the algorithms, models, and derivations that go into both filters is presented. With this simulation and specific sensor selection the position of the chaser spacecraft relative to the target can be estimated to within about 5 m, the velocity to within .1 m/s, and the attitude to within 2 degrees for both filters. If a thrust is applied to the IMU measurements, it takes about 1.5 minutes to get a good position estimate, using the Extended Kalman Filter with Uncompensated Bias. The error settles almost immediately using the general Extended Kalman Filter. These filters have been designed for and can be implemented on almost any small, low cost, low power satellite with this inexpensive set of sensors.Aerospace Engineering and Engineering Mechanic

Bridging the Gap: Collaboration using Nanosat and CubeSat Platforms Through The Texas 2 STEP (2 Satellite Targeting Experimental Platform) Mission

The Texas 2-STEP (2-Satellite Targeting Experimental Platform) mission is the University of Texas at Austin\u27s (UTAustin) entry into the University Nanosat-5 (UNP-5) competition, a program sponsored by the Air Force Research Laboratory (AFRL), NASA and the American Institute of Aeronautics and Astronautics. The 2-STEP mission is to perform an autonomous rendezvous and formation flight demonstration using an innovative and inexpensive GN&C system. Two vehicles will be launched in a joined configuration but will perform a separation maneuver on-orbit to drift apart to a distance of 3 kilometers. When commanded, the larger, actively controlled Chaser nanosatellite will autonomously maneuver back to within 100 meters of the smaller, passively controlled Target. The Target vehicle is designed based on the CubeSat platform, a design solution that merges the Nanosat and CubeSat programs in a unique collaboration that has not been previously demonstrated. A standard CubeSat platform has been designed using commercial hardware which can be adapted for a 1U (1-Unit), 2U or 3U CubeSat mission. Use of the CubeSat standard is a responsive space solution that incorporates a modular vehicle design for use in multiple university missions. Adoption of this standard also promotes collaboration between Satellite Design Laboratory programs at UT-Austin. This paper will review the Texas 2-STEP mission and highlight how the Target vehicle is bridging a gap between the Nanosat and CubeSat communities. Elements of vehicle design as well as Chaser-Target team cooperation will also be covered