ISS Utilization: SCaN
ISS Utilization - SCaN (Space Communications and Navigation) Testbed
The growth of SDR (Software Defined Radio) technology offers NASA the opportunity to improve the way space missions develop and operate space transceivers for communications, networking, and navigation. Reconfigurable SDRs with communications and navigation functions implemented in software provide the capability to change the functionality of the radio during a mission and optimize the data capabilities (e.g. video, telemetry, voice, etc.). The ability to change the operating characteristics of a radio through software once deployed to space offers the flexibility to adapt to new science opportunities, recover from anomalies within the science payload or communication system, and potentially reduce development cost and risk through reuse of common space platforms to meet specific mission requirements. SDRs can be used on space-based missions to almost any destination. 1)
CoNNeCT (Communications, Navigation, and Networking reConfigurable Testbed)
CoNNeCT is a NASA project with the objective to provide an on-orbit, adaptable, SDR (Software Defined Radio) facility located on ISS (International Space Station) along with the corresponding ground and operational systems. These facilities will enable experiments and technology development to conduct a suite of communications experiments. 2) 3)
Internal to NASA, the “CoNNeCT” Project is funded to develop the Flight (space-based) and Ground (terrestrial-based) Systems, and to conduct mission operations.
External to NASA and for ISS operations, CoNNeCT is known as "SCaN Testbed" since the astronauts and ground operators needed a more specific name to avoid confusion.
The SCAN Testbed will be launched from Japan and is designed to operate for a minimum of two years.
The growth of SDR technology offers NASA the opportunity to improve the way space missions develop and operate space transceivers for communications, networking, and navigation. Reconfigurable SDRs with communications and navigation functions implemented in software provide the capability to change the functionality of the radio during a mission and optimize the data capabilities (e.g. video, telemetry, voice, etc.). The ability to change the operating characteristics of a radio through software once deployed to space offers the flexibility to adapt to new science opportunities, recover from anomalies within the science payload or communication system, and potentially reduce development cost and risk through reuse of common space platforms to meet specific mission requirements. SDRs can be used on spaceborne missions to almost any destination.
Mission objectives of the CoNNeCT project: The CoNNeCT Project will provide NASA, industry, other Government agencies, and academic partners the opportunity to develop and field communications, navigation, and networking technologies in the laboratory and space environment based on reconfigurable, software defined radio platforms and the STRS (Space Telecommunications Radio System) architecture. The CoNNeCT Project Experiments Program will devise, solicit, and conduct on-orbit experiments to validate and advance the open architecture standard for SDRs; advance communication, navigation, and network technologies to mitigate specific NASA mission risks and to enable future mission capabilities.
Identified are several research and technology areas the SCAN Testbed was designed to support:
• Software Defined Radios operating at S-, L-, and Ka-band
• On-board data management function and payload networking
• Radio Science experiments using the unique capabilities of the SDRs
• Precise Navigation and Timing.
The SCaN Testbed has been designed and built at NASA/GRC (Glenn Research Center) in Cleveland, Ohio. 4)
Figure 1: Overview of the SCaN Testbed communication links (image credit: NASA)
Launch: The SCaN Testbed was launched to the space station on July 21,2012 on from TNSC (Tanegashima Space Center) of JAXA, Japan on the launch vehicle H-IIB No 3. The cargo transfer vehicle was HTV-3 (nicknamed Kounotori3), which contained the SCaN Testbed as well as other cargo for the ISS and JEM. 5)
Orbit: ISS orbit at a nominal altitude range of 360-460 km, inclination = 51.6º.
ISS and HTV integration: A standard ISS integration approach is used via the JSC (Johnson Space Center) PIM (Payload Integration Manager), with some extension of prior work since CoNNeCT is the first ELC payload installed on-orbit. The carrier physical interfaces are depicted in Figure 2 and the HTV launch processing is shown in Figure 3. The HTV delivers its cargo to the vicinity of the ISS where the ISS robotic arm operations conduct many transfers and installation.
Figure 2: ISS and HTV carrier interfaces (image credit: NASA)
Figure 3: HTV launch site processing (image credit: NASA)
SCaN Testbed location on ISS:
After ISS arrival and berthing of HTV-3, the SCAN Testbed will be transferred and installed via EVR (Extravehicular Robotics) to the ELC-3 (ExPRESS Logistics Carrier-3) in the inboard, ram-facing, zenith-facing payload location on an exterior truss of the ISS (Figure 4). The Testbed relies on the ISS ExPA (Express Pallet Adapter) to provide standardized structural, electrical and data interfaces with the ISS ELC (ExPRESS Logistics Carrier), the SSRMS (Space Station Remote Manipulator System), and the JAXA (Japanese Aerospace Exploration Agency) EPMP (Multipurpose Exposed Pallet). The SCaN Testbed location on the ISS is shown in Figure 4. 6) 7) 8) 9)
Figure 4: Illustration of the SCaN Testbed location on the ISS (image credit: NASA)
The SCaN Testbed will consist of reconfigurable and reprogrammable SDR (Software Defined Radio) transceivers/transponders operating at S-band, Ka-band, and L-band, along with the required RF/antenna systems necessary for communications. Designed to operate for a minimum of two years, the three SDRs will provide S-band duplex RF (Radio Frequency) links directly with the ground, [also referred to as the Near Earth Network (NEN)], S-band duplex RF links with the TDRSS (Tracking and Data Relay Satellite System), [also referred to as the Space Network (SN)], Ka-band duplex with TDRSS, and L-band receive-only with the GPSS (Global Positioning Satellite System). The SCaN Testbed will be in low earth orbit and has multiple antennas providing connectivity to a series of NASA Space Network (SN) TDRSS satellites in geosynchronous orbits and NASA Near Earth Network (NEN) stations. The major components of the SCaN Testbed are shown in Figure 5.
The SCaN Testbed uses a frequency assignment between ISS and TDRS at S-band and Ka-band to send and receive data from the radios and antenna system. SCaN Testbed commands are sent from the CoNNeCT Control Center located within the GRC Tele-Science Support (TSC) to the radios to configure and operate each radio. Communication with the SCaN Testbed through ISS is considered the primary path, this includes the wired path between the SCaN Testbed and ISS and the wireless path from ISS to the WSC (White Sands Complex ). The WSC is wired to the remaining ground station facilities consisting of the HOSC (Huntsville Operations Center), the NISN (NASA Integrated Service Network), and the CCC (CoNNeCT Control Center) located at GRC (Glenn Research Center), the CoNNeCT Experiment Center (CEC) is also part of the CCC.
A RF data connection will provide a direct bi-directional connection between the radios and ground stations. This second communication path (commanding and bidirectional data) is the experimental link with the SN and the NEN, this is the wireless path between the SCaN Testbed and Ground Stations such as the Wallops Ground Station. The TSC facility, located at GRC, allows payload developers and scientists on Earth to monitor and control experiments onboard the ISS (International Space Station). Data from the radios are received at the White Sands Complex, Las Cruces, NM via TDRS and routed to GRC. For Global Positioning System (GPS) experiments, the JPL radio is configured to receive and process GPS signals. Data is collected on-board and sent to ground via TDRS or the primary path.
SCaN Testbed Design and SDRs (Software Defined Radios):
At the core of the SCaN Testbed are three unique SDRs (Software Defined Radios) provided by government and industry partners. All of the radios are compliant with the NASA Space Telecommunications Radio System (STRS) Architecture Standard. The SCaN Testbed also includes an avionics subsystem, RF switching, and a variety of antennas, two of which are on a gimbal.
The three SDRs developed by JPL (Jet Propulsion Laboratory), GD (General Dynamics) and Harris Corporation each adhere to the functional diagram in Figure 7. The functional diagram illustrates three key elements of each SDR: a GPM (General purpose Processor Module), a SPM (Signal Processing Module), and the RFM (Radio Frequency Module). Each SDR is consistent with this type of architecture; however, specific implementations differ for each radio (Ref. 3). 11) 12)
The GPM contains the general purpose processor and associated memory elements for application processing and radio control. The STRS OE (Operating Environment) runs within the GPM to control the waveforms and other radio functions and platform services throughout the SPM and RFM. The GPM controls loading the waveform from persistent memory, e.g. EEPROM (Electrically Erasable Programmable Read-Only Memory), into the processor of FPGA as designed. Portions of the waveforms can run within the GPM or SPM and are abstracted from the underlying hardware by the STRS standard. The SPM includes the hardware for the high speed signal processing performed in each radio.
Figure 6: Illustration of the three SDR platforms (image credit: NASA)
The GD (General Dynamics) SDR is S-band only, while the JPL (Jet Propulsion Laboratory) SDR has both S-band and L-band (GPS) capability. The HC (Harris Corporation) SDR is Ka-band. The operating systems and waveforms within these radios are reconfigurable and will be changed (modified or replaced) during on-orbit operations. The avionics subsystem provides general control and data handling, as well as supporting network routing. Just like the radios, the software loaded in the avionics subsystem will be changed for experiments. The radios are mounted to the Flight Enclosure and functionally interface with the avionics and RF (Radio Frequency) subsystems.
Figure 7: General SDR functional architecture (image credit: NASA)
The STRS OE manages the functions within the SDR, including command and telemetry, inter-process communications among software elements, and control functions such as loading and unloading the waveforms from memory and executing the waveform. The key element of the software architecture is the application programming interface abstraction between the waveform application and the underlying hardware. User applications access the RTOS (Real-Time Operating System) of the operating environment through a POSIX (Portable Operating System Interface for Unix) interface and the waveforms access remaining OE functions through a set of APIs (Application Programming Interfaces) defined by the STRS architecture (STRS API).
Once a user waveform application is loaded on a platform, the POSIX and STRS APIs provide the software interfaces to the underlying hardware. On the firmware interfaces within the FPGA, the STRS standard calls out requirements for FPGA signal abstractions between the application and the platform hardware provided by the platform developer and certain documentation of abstractions for hardware resources (e.g., FPGA, DAC, ADC) available for future waveform developers.
Table 1: Overview of SDR platform characteristics
The SCaN office at NASA has developed an architecture standard for SDRs used in spaceborne and ground-based platforms to provide commonality among radio developments to provide enhanced capability and services while reducing mission and programmatic risk. The STRS (Space Telecommunications Radio System) architecture standard defines common waveform software interfaces, methods of instantiation, operation, and testing among different compliant hardware and software products. These common interfaces within the architecture abstract, or remove, the application software from the underlying hardware to enable technology insertion independently at either the software or hardware layer.
SCaN technology objectives:
• Antenna technology: - The focus of this effort is on Ka-band transmit antenna arraying. The adaptive beamforming technique will be equally applicable to the DSN (Deep Space Network) and to spacecraft systems.
• DTN (Disruption Tolerant Networking): - The DTN program establishes a long-term, readily accessible communications test-bed onboard the ISS (International Space Station). Two CGBA (Commercial Generic Bioprocessing Apparatus), CGBA-5 and CGBA-4, will serve as communications test computers that transmit messages between ISS and ground Mission Control Centers.
• iROC (Integrated RF and Optical Communications): - Given the strong and continued momentum of development in the RF domain, what can be done from an integration standpoint to optically enhance the performance of a deep-space RF communications system.
• Ka-band atmosphere: - Statistical characterization of the diurnal, annual and secular path length fluctuations at candidate sites for future distributed ground based antenna systems operating at Ka-band applicable to all three of NASA’s current space communication ground communication networks.
• STRS (Space Telecommunications Radio System): - NASA’s SCaN Office has developed an architecture standard for SDRs used in space and ground-based platforms to provide commonality among radio developments to provide enhanced capability and services while reducing mission and programmatic risk.
Among other items, the ExPA includes the active portion of a FRAM (Flight Releasable Attachment Mechanism), power and data connector panels, EVA (Extravehicular Activity) robotic interfaces and the payload adapter plate. The ExPA serves as the foundation of the CoNNeCT flight system.
Figure 8: Flight system without ExPA and non-radiating panels (image credit: NASA)
Table 2: SCaN Testbed parameters
Mechanical subsystem: It provides structural support for the other subsystems; its design also allows thermal energy to be rejected to space via three radiating surfaces. The subsystem consists of a frame-and-panel flight enclosure, various mounting brackets, fasteners, and multilayer insulation on the two non-radiating exposure surfaces. The mechanical subsystem accounts for ~39% of the 365 kg Flight System mass.
The Flight System is composed of the following four subsystems which are integrated on the ExPA: Avionics subsystem, RF subsystem, Antenna subsystem, and SDR (Software Defined Radios) as shown in Figure 10.
Avionics subsystem: The avionics subsystem provides the electrical and command & data handling interface between ISS systems and the SCaN Testbed systems. These interfaces include power distribution and control, grounding and isolation, communication (commanding and data) interfaces with ISS, flight system health and status, and SCaN Testbed subsystem communications and control as shown in Figure 9. The GSE (Ground Support Equipment) interface is for pre flight test only.
Electrical subsystem: It receives a maximum of ~ 500 W of electrical power from the ExPA, conditions it and transfers it to the electrical loads in the system. Digital communication between subsystems and overall system command and control is also provided by the subsystem. The electrical subsystem is comprised of 3 primary subassemblies [avionics, a TWTA PSU (Power Supply Unit), and TCA (Thermostat Control Assembly)] plus resistance heaters and the cabling interconnecting all of the subsystems. Functional interaction of the avionics portion of the electrical subsystem and other elements of the Flight System is shown in Figure 10.
Figure 9: Block diagram of the avionics subsystem (image credit: NASA)
The avionics subsystem provides the command & data handling interface between ISS systems and the SCaN Testbed systems. These interfaces include power distribution and control, grounding and isolation, communication (commanding and data) interfaces with ISS, flight system health and status, and SCaN Testbed subsystem communications and control. The GSE (Ground Support Equipment) interface is for pre flight test only.
The C&DH (Command & Data Handling) subsystem uses a 733 MHz processor and 64 GB of flash memory to operate the Flight System. SpaceWire and MIL-STD-1553 buses are employed for command and telemetry as well as data flow. Each SDR has a command and control interface and data communications interface. The GD and JPL SDRs use MIL-STD-1553 for command and control and SpaceWire for the data interface. The Harris SDR has two separate SpaceWire interfaces, one for command/control and one for data. The RF subsystem TWTA (Traveling Wave Tube Amplifier and coax switches are controlled through discrete digital lines. The Antenna Pointing System GCE (Gimbal Control Electronics) also interfaces with the avionics package for command and control through a MIL-STD-1553 interface.
Figure 10: Block diagram of the Flight System (image credit: NASA)
RF subsystem: It consists of an RF plate subassembly, a TWTA (Traveling Wave Tube Amplifier), five antennas and interconnecting transmission cable and waveguide. The RF plate subassembly contains a Ka-band isolator and attenuator and three coaxial transfer switches to route signals to and from different S-band antennas. Two low-gain S-band antennas and an L-band antenna are installed stationary with respect to the flight system. The medium-gain S-band antenna and the high-gain Ka-band antenna are jointly housed on an articulating arm for pointing. The RF subsystem and its interfaces are illustrated in Figure #. The functional interactions of the RF subsystem are also shown in Figure 10.
APS (Antenna Pointing Subsystem): The APS is used to point the medium-gain S-band and high-gain Ka-band antennas for communication with the TDRSS. In addition to a launch restraint and thermal control resistance heaters, two other main subassemblies combine to complete the APS: the IGA (Integrated Gimbal Assembly) and the GCE (Gimbal Control Electronics). The IGA contains two rotary actuators - one each for local elevation and azimuth adjustment.
The actuators in combination with the arm mechanism, in which they are housed, enable precision pointing of the antennas over a large viewing area. Restrained by physical hardstops to limit irradiation of ISS elements, the IGA rotation spans 174º in elevation and 76º in azimuth. The resultant boresight sweep limits are shown in Figure 11. This FOV allows the testbed to satisfy key availability requirements for monthly TDRS (Tracking and Data Relay Satellite) contacts.
Using a MIL-STD-1553 interface, the GCE provides the power, control and telemetry path between the IGA and the avionics subassembly. Position and rate commands are sent from the avionics software to the GCE which then translates and sends the appropriate step commands to the actuators. Optical encoders on each actuator provide position indication telemetry that is transferred through the GCE to the avionics. Because of the wide beam width of the medium-gain antenna, the TDRS S-band links are easily established using open-loop pointing algorithms in the avionics software. However, for Ka-band communication with TDRS, closed-loop control based on signal feedback from the Harris SDR is used to accurately point and track using the APS.
Figure 11: Schematic view of boresight sweep limits (image credit: NASA)
SCaN Testbed status:
• March 2013: The project completed the first round of SDR commissioning operations. The overarching objectives of SDR Commissioning are to verify the end-to-end data flow of the SCaN Testbed and ground systems, and to verify that the radio links’ performance is predictable. SDR Commissioning activities are really the beginning stages of the in-house experiments, by virtue of the launch waveforms going through more operating hours. Support from White Sands (WSC) and the Space Network has been excellent, as inline measurements and delogs at WSC are not typical services for Ka-band users. Thanks to the team for supporting the Commissioning here at GRC and WSC. They worked long hours and through the weekend too. 13)
Mission Operations Network Overview:
The Ground System consists of the CCC (CoNNeCT Control Center), the CEC (CoNNeCT Experiment Center), the GFV (Ground Verification Facility), and the external ground systems and their interfaces located at HOSC (Huntsville Operations Support Center), WSC (White Sands Complex), and WGS (Wallops Ground Station). The NISN (NASA Integrated Services Network) is the network that connects these entities. Other ground stations beyond WGS may also be used during operations, including White Sands 1, or user supplied ground stations. However, WGS is currently the baseline station and was used for operations planning and link analysis.
The SCaN Testbed and Ground System send and receive commands and data, and manipulate (stores, routes, and processes) data. The Flight System and Ground System interface with external systems to send and receive RF signals to and from space. The RF signals carry commands and data between the two CoNNeCT elements. The Ground System provides terrestrial control of the Flight System through the CoNNeCT Control Center, a top-level schematic of the Ground System is shown in Figure 12.
Figure 12: SCaN Testbed Ground System (image credit: NASA)
Primary communication path elements: There are two communication paths for the CoNNeCT mission. The primary communications path (commanding and telemetry) will exist through the ISS S-band and Ku-band links. This link will be coordinated through HOSC at MSFC (Marshall Space Flight Center). The HOSC will receive the data from the SN and forward it to the GRC (Glenn Research Center) CCC (CoNNeCT Control Center) through existing architecture.
The SCaN Testbed uses both the primary and experimental paths for commanding. Nominal commanding will use the primary path. Commands will originate from the GRC TSC except for 13 critical commands. The critical commands will be sent by the PRO (Payload Rack Officer) from the HOSC. The critical commands will reside only in the POIC (Payload Operations Integration Center) database. In the future the SCaN Testbed will have the capability to use its RF links to send non-critical commands through the SDRs to the Avionics.
HOSC/POIC: The POIC, located within MSFC's HOSC (Huntsville Operations Support Center), houses the ground systems for managing the execution of on-orbit ISS (International Space Station) payload operations including telemetry, command, voice, video, information management, data reduction, and payload planning systems. All POIC ground systems are distributed to the CCC.
The POIC contains several data and network systems that provide various capabilities: The PDSS (Payload Data Services System) is used to receive, process, store (for 2 years), and distribute ISS 150 Mbit/s payload telemetry data to the POIC, International Partners, Telescience Support Centers and other remote user facilities.
The EHOSC (Enhanced Huntsville Operations Support Center) performs command processing and real-time and near real-time telemetry processing for simulation, training, and flight operations.
The PPS (Payload Planning System) provides a set of software tools to automate the planning, scheduling, and integration on ISS payload operations during pre-increment planning, weekly planning, and real-time operations execution.
Experiment Communication Path Elements: The second communication path (commanding and bidirectional data) is the experimental link with the SN and the NEN. This link will be scheduled directly by the CCC with the supporting elements. This link includes S-band and Ka-band services to the Space Network and S-band to the NEN. Users will coordinate their ground station use with the CCC.
• Forward Link: GRC CCC through NISN to White Sands to TDRSS to SCaN Testbed
• Return Link: SCaN Testbed to TDRSS to White Sands through NASA Integrated Services Network NISN to GRC CCC
• Uplink: GRC CCC through NISN to Ground Station (e.g. WFF) to SCaN Testbed
• Downlink: SCaN Testbed to Ground Station (e.g. WFF) through NISN to GRC CCC.
Figure 13: Functional diagram of the CCC (CoNNeCT Control Center), image credit: NASA
Experiment operations: Once on-orbit, the CoNNeCT SCaN Testbed will be available to experiments from NASA, industry, academia and other organizations. Based on announcement of opportunities offered by NASA, experimenters will propose investigations to conduct using the SCaN Testbed. The experiments will entail new software applications that run on the SDRs or within the flight computer (avionics) along with experiment specific ground hardware or software. The experiment software applications will demonstrate new communications signal formats (e.g., modulation, coding), networking (e.g., on-board routing and DTN) and assessment of navigation techniques based on GPS signals at L1, L2, and the emerging L5 GPS frequencies.
Once a proposal is submitted to NASA, an Experiment Review Board will assess the objectives and advancements proposed and recommend experiments for use with the SCaN Testbed that meet the solicitation criteria. Once approved, experimenters will begin development of their new experiment application and ground hardware. After development has progressed beyond the design and initial development stage, experimenters will be provided access to the SDR and avionics breadboards and engineering models at NASA/GRC to continue, refine and complete their waveform or avionics application development. When an experimenter completes their SRD application, the waveform will be tested for STRS compliance and verified for operation with the flight system. After verification, the application software will be uploaded to the flight system for on-orbit experiment operations.
To conduct the on-orbit portion, experimenters will generally work form the Experiment Center at NASA/GRC, working closely with the CCC (CoNNeCT Control Center). Experiment specific ground hardware will reside at the CEC (CoNNeCT Experiment Center). The CEC is linked to the SN (Space Network) Control Center where experiment data is exchanged with the WSC (White Sands Complex) and transmitted to CoNNeCT via TDRSS. Experimenter hardware will send and receive data directly with the SCaN Testbed through the CoNNeCT ground system infrastructure.
Figure 14: Experimenter-TDRSS interfaces (image credit: NASA)
As shown in Figure 14, the experiment data links at Ka-band and S-band exist between CoNNeCT and NASA's TDRSS and WSC ground station or may use an S-band direct to ground link (not shown in Figure 14). During pre-flight testing, simulators are used for the ELC interface and ISS command processing.
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2) “Communications, Navigation and Networking re-Configurable Testbed (CoNNeCT/SCAN Testbed),” NASA, Feb. 10, 2012, , URL: http://spaceflightsystems.grc.nasa.gov/SpaceOps/CoNNeCT/
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5) “Launch Result of H-IIB Launch Vehicle No. 3 with H-II Transfer Vehicle "KOUNOTORI3" (HTV3) Onboard,” JAXA, July 21, 2012, URL: http://www.jaxa.jp/press/2012/07/20120721_h2bf3_e.html
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7) “Technology Overview and Operations Concept for SCaN Testbed,” NASA/GRC, June 2011, URL: http://spaceflightsystems.grc.nasa.gov/.../Ops%20Con%20for%20SCAN%20Testbed_SBIR.pptx
8) “Unique Testbed Soon Will Be in Space,” NASA, Feb. 9, 2012, URL: http://www.nasa.gov/centers/glenn/exploration/Connect.html
9) Richard Reinhart, Sandra Johnson, James Lux, Greg Heckler, Jacqueline Myrann, “SCAN Testbed, Overview and Opportunity for Experiments,” ISS Research & Development Conference, Denver CO, USA, June 26-28, 2012, URL: http://spaceflightsystems.grc.nasa.gov/.../SCAN%20Testbed,%20Overview%20and%20Opportunity%20
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11) Courtney B. Duncan, David E. Robison, Cynthia Lee Koelewyn, “Software Defined GPS Receiver for International Space Station,” ION 2011 International Technical Meeting, Session 4 'Remote Sensing Using GNSS,' San Diego, CA, USA, January 24-26, 2011
12) Thomas Kacpura, Richard Reinhart, Sandra Johnson, “Software Defined Radio Developments and Verification for Space Environment on NASA’s Communication Navigation, and Networking Testbed (CoNNeCT),” IDGA’s (Institute for Defense and Government Advancement)Cognitive Radio Summit, Washington DC, USA, February 27-29, 2012, URL: https://spaceflightsystems.grc.nasa.gov/.../SDR%20Developments%20and%20Verification%20
13) “Space Communications and Navigation Testbed (SCAN Testbed),” NASA, April 3, 2013, URL: http://www.nasa.gov/mission_pages/station/research/experiments/162.html#images
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.