Synchronized Position, Hold, Engage, Reorient, Experimental Satellites - VERTIGO (SPHERES-VERTIGO) - 08.27.15

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
The Synchronized Position, Hold, Engage, Reorient, Experimental Satellites – VERTIGO (SPHERES-VERTIGO) investigation uses the SPHERES facility free-flying satellites and is designed to demonstrate and test, in a complex environment, enhanced technologies and techniques related to visual inspection and navigation. This effort incorporates hardware and software that enables multiple SPHERES to construct three dimensional (3D) models of a target object. Additionally, this investigation explores how well the SPHERES free-flyers then perform relative navigation solely by reference to these 3D models.
Science Results for Everyone
Information Pending

The following content was provided by David W. Miller, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom:

Principal Investigator(s)
David W. Miller, Ph.D., Massachusetts Institute of Technology, Cambridge, MA, United States

Co-Investigator(s)/Collaborator(s)
John J. Leonard, Massachusetts Institute of Technology, Cambridge, MA, United States
Alvar Saenz-Otero, Ph.D., Massachusetts Institute of Technology, Cambridge, MA, United States

Developer(s)
Aurora Flight Sciences Corporation, Cambridge, MA, United States
NASA Ames Research Center, Moffett Field, CA, United States
Massachusetts Institute of Technology, Cambridge, MA, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
National Laboratory - Department of Defense (NL-DoD)

Research Benefits
Information Pending

ISS Expedition Duration 1
September 2012 - September 2015

Expeditions Assigned
33/34,35/36,37/38,39/40,41/42,43/44

Previous ISS Missions
Information Pending

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Experiment Description

Research Overview

  • The SPHERES-VERTIGO investigation uses the SPHERES platform on International Space Station (ISS) and is designed to demonstrate stereo visual inspection in order to assess close proximity inspection and navigation.
  • The SPHERES-VERTIGO investigation software incorporates computer vision based navigation and mapping algorithms capable of building a three-dimensional map of another object and performing relative navigation solely by reference to this three-dimensional model.
  • The space object to interact with is assumed to be moving and possibly tumbling, and its state will not be known a priori to the observer SPHERES.
  • Once a 3D model of the object is constructed, the two observer SPHERES will perform relative navigation solely by sensory reference to the target object and its 3D model.
  • In order to test these algorithms, hardware upgrades to the SPHERES facility satellites includes cameras, an upgraded processor, a high-speed communications system and additional batteries.

Description
The SPHERES facility onboard ISS provide a unique lower iterative risk, , long duration microgravity research facility capable of supporting iterative, quick reaction testing of technologies in support of DoD and NASA missions. Under the auspices of the ISS-Hosted SPHERES Integrated Research Experimentation (InSPIRE) program, the SPHERES-VERTIGO investigation increases the scope of the SPHERES facility by adding hardware and developing new algorithms to execute investigations and tests of new critical technologies.

The ability for a spacecraft to autonomously map a cooperative or non-cooperative object and localize itself with respect to that object is an enabling technology for a number of satellite servicing, inspection, repair and orbital debris removal missions. These types of problems can typically be solved using algorithms from the Simultaneous Localization and Mapping (SLAM) field of study. Many typical SLAM algorithms make the assumption that the environment that they are mapping is stationary. However, prior studies have estimated that there are over 100 potential space objects near the Geostationary Orbit belt that are spinning at rates over 20 rotations per minute.

Applying SLAM techniques to objects that are spinning at high rates will typically violate a number of the fundamental and underlying assumptions of these algorithms. For example, the object of interest is not an inertial frame of reference and therefore the motion of the inspection spacecraft in an inertial frame (where its dynamics can be accurately modeled) is unobservable without incorporating additional sensors. Additionally, since both planning and estimation algorithms require propagating the state of dynamic models, it is important to estimate the linear and angular velocities of both the space object and inspection vehicle in an inertial frame.

The SPHERES-VERTIGO program plans to develop and modify algorithms for a number of aspects of the SLAM problem that are capable of handling unknown and non-cooperative space objects (i.e. a space object that is unable to provide its own attitude control relative to another object) that are spinning at high speeds. Specifically, the proposed approach will map an object with little to no apriori information using stereo cameras and localize itself and the object within an inertial frame. Additionally, it will estimate the linear and angular velocities of the object and servicer-type vehicle as well as it’s principal inertial axes, center of mass location and relative moments of inertia.

In order to properly simulate a spinning and nutating object, the SPHERES satellites have been upgraded to include stereo cameras and a high performance embedded computer. The algorithms that are developed will be tested in the microgravity environment of the International Space Station using this testbed.

The SPHERES-VERTIGO investigation uses the SPHERES facility, which consists of three self-contained satellites (i.e., SPHERES). Each satellite is an 18-sided polyhedron that is 0.2 meter in diameter and weighs 3.5 kilograms. Individual satellites contain an internal propulsion system, power, avionics, software, communications, and metrology subsystems. The propulsion system uses carbon dioxide (CO2), which is expelled through the cold gas thrusters. SPHERES satellites are powered by AA batteries.

SPHERES-VERTIGO unique hardware consists of two VERTIGO Goggles, and supporting hardware that includes diagnostic and data interface equipment and cables, a visual calibration target, protective glasses, and textured target SPHERES stickers. Each VERTIGO Goggles consists of an avionics stack, a detachable optics mount, a control panel, two SATA flash hard disks, two wireless network antennas, and an ISS Nikon battery receptacle. A Nikon EN-EL4A battery will be used to power the VERTIGO Goggles.  Each VERTIGO Goggles will attach to a SPHERES satellite via its Expansion Port. Each VERTIGO Goggles is approximately 11.6cm X 17.9cm X 15.3cm and weighs 1.6 kilograms.

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Applications

Space Applications
The ability to create a three-dimensional model of an unknown object in space using only one or two small satellites is an enabling technology applicable to a wide range of space missions. One of the program’s planned principal contributions is to determine how to perform autonomous inspection and mapping of a tumbling and spinning object. Although many spacecraft that are launched today are three-axis stabilized, there is a significant number of spacecraft that were designed to be spin-stabilized. A few examples are the Hughes Spacecraft 376, which was spun at 50 rotations per minute (RPM). Additionally, the interplanetary cruise stages of DAWN, JUNO and MSL were spun at 48, 5 and 2 RPM respectively.
In 2010, a study was published by Kaplan et. al. (AIAA Space 2010) which assessed the required technologies to perform space debris capture. Included in this study was an analysis of the distribution of space objects and their angular velocities. The authors concluded that in orbits below 500 km, the gravity gradient and atmospheric pressure would provide enough torque to null the spin rates over long enough periods of time. However, in Geostationary Orbit (GEO) and near-GEO (i.e. graveyard orbits), the authors state that "it is reasonable to estimate that there are over 100 large expired satellites that are still rotating at several 10s of RPM." The ability to perform proximity operations with spinning spacecraft in GEO will become more important as time goes on since this is a very important location for the telecommunications and earth-observation satellite industry.
 

Earth Applications
N/A

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Operations

Operational Requirements
The SPHERES facility is allocated a number of test sessions per ISS Increment. Four test sessions will be utilized by SPHERES-VERTIGO as the facility user. As the facility lead, NASA Ames will determine specific test session scheduling based on ongoing planning and research results.

Operational Protocols
A typical SPHERES-VERTIGO test session will consist of:

  • Uplink algorithms one week before the test session.
  • Unstow and configure SPHERES facility satellites and work area.
  • Attach and configure the SPHERES-VERTIGO hardware to the SPHERES satellites.
  • Load algorithms onto the SPHERES through the communication system.
  • Load programs to the VERTIGO Goggles via Ethernet cable connected to the ISS ELC laptop.
  • Run individual VERTIGO Goggles tests using the ISS laptop.
  • Downlink of the data for post-session assessment.

Once the data is analyzed, algorithms are revised, and the next test session is scheduled.

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Results/More Information

The SPHERES-VERTIGO test runs were conducted aboard the ISS on February 26 and March 12 of 2013 during Expedition 34. The first test revealed problems due to higher than expected velocity measurement noise levels via the stereo camera system which caused too many thruster firings. Adjustments were made and tests were continued. Despite a few anomalies, the SPHERES vehicle with the VERTIGO stereo camera installed was able to demonstrate a complete autonomous circumnavigated inspection trajectory around a target object (Fourie 2013).

 

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Results Publications

    Fourie D, Tweddle BE, Ulrich S, Saenz-Otero A.  Vision-based relative navigation and control for autonomous spacecraft inspection of an unknown object. 2013 AIAA Guidance, Navigation, and Control Conference, Boston MA; 2013 August 19-20 17 pp.

    Fourie D, Tweddle BE, Ulrich S, Saenz-Otero A.  Flight results of vision-based navigation for autonomous spacecraft inspection of unknown objects. Journal of Spacecraft and Rockets. 2014 May 8; epub: 11 pp. DOI: 10.2514/1.A32813.

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Ground Based Results Publications

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ISS Patents

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Related Publications

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Related Websites
MIT Space Systems Laboratory
MIT Space Systems Laboratory
MIT Space Systems Lab YouTube Channel

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Imagery

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The SPHERES-VERTIGO investigation setup showing tracking (with goggles) and target SPHERES (MIT Development Team).


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The SPHERES-VERTIGO imaging goggles detached from the SPHERES facility (MIT Development Team).


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The SHPHERES-VERTIGO goggles assembly attached to a SPHERES device for air table testing (MIT Development Team).


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The SPHERES-VERTIGO goggles assembly attached to a SPHERES satellite during final hardware checkout (MIT Development Team)


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The SPHERES-VERTIGO goggles assembly onboard the International Space Station with Astronaut Thomas Marshburn during its first operations (NASA)


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The SPHERES-VERTIGO goggles assembly onboard the International Space Station with Astronaut Thomas Marshburn during its first operations (NASA)


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