Progressive development of microsatellite technologies has resulted in increased demand for lightweight electrical power subsystems including solar arrays. The use of thin film photovoltaics has been recognized as a key solution to meet the power needs. The lightweight cells can generate sufficient power and still meet critical mass requirements. Commercially available solar cells produced on lightweight substrates are being studied as an option to fulfill the power needs. The commercially available solar cells are relatively inexpensive and have a high payoff potential. Commercially available thin film solar cells are primarily being produced for terrestrial applications. The need to convert the solar cell from a terrestrial to a space compatible application is the primary challenge. Solar cell contacts, grids and interconnects need to be designed to be atomic oxygen resistant and withstand rapid thermal cycling environments. A mechanically robust solar cell interconnect is also required in order to withstand handling during fabrication and survive during launch. The need to produce the solar cell interconnects has been identified as a primary goal of the PowerSphere program and is the topic of this paper. Details of the trade study leading to the final design involving the solar cell wrap around contact, flex blanket, welding process, and frame will be presented at the conference.
Research Containing: Technology demonstration
The MIT Space Systems Laboratory has developed the Synchronized Position Hold Engage and Reorient Experimental Satellites (SPHERES) facility for the testing of formation flight and autonomous docking algorithms inside the International Space Station (ISS), in NASA's reduced gravity aircraft and in a 1-g laboratory environment. To provide SPHERES with reliable and accurate position, velocity, attitude and angular rate estimation, an innovative state estimation system based on ultrasound transmission has been developed. An extended Kalman filter (EKF) processes time-of-flight data collectedby ultrasonic receivers, as well as angular rate measurements provided by gyroscopes, to compute the state estimates required by the satellites when maneuvering. To increase the robustness of the system, the EKF has been augmented with a fault detection capability that uses the filter innovation (residual) to diagnose measurement errors. Two versions of the algorithm were successfully implemented and used on the SPHERES facility onboard the ISS during a series of five test sessions, from May 2006 to November 2006. This paper describes both versions in detail, along with di culties encountered during the implementation on the hardware and their solution. Results from experiments performed in the ISS to validate the algorithms are also presented.
The deployment of space robots for servicing and maintenance operations that are teleoperated from the ground is a valuable addition to existing autonomous systems, because it will provide flexibility and robustness in mission operations. In this connection, not only robotic manipulators are of great use, but also free-flying inspector satellites supporting the operations through additional feedback to the ground operator. The manual control of such an inspector satellite at a remote location is challenging, because navigation in three-dimensional space is unfamiliar and large time delays can occur in the communication channel. This paper shows a series of robotic experiments, in which free flyers are controlled by astronauts aboard the International Space Station (ISS). The Synchronized Position Hold Engage Reorient Experimental Satellites (SPHERES) were utilized to study several aspects of a remotely controlled inspector satellite. The focus in this case study is investigating different approaches to human–spacecraft interaction with varying levels of autonomy under zero-gravity conditions.
Current research on control allocation emphasizes reconfiguration for adapting to thruster failures. However, in the application of autonomous assembly, the reconfiguration is necessitated by changing physical properties. For the scenario of an assembler tug constructing a large space structure, every docking and undocking maneuver used for the tug to move an individual payload causes a large shift in the dynamics of the tug. Not only do the mass properties change, but so does the thruster configuration. Changes in the center of mass, mass, and inertia of the tug-payload system, causes changes in the equivalent force exerted by each thruster. This paper explores reconfigurable control allocation to adapt to changes in the mass properties. Specifically considered are changes to the center of mass and thruster configuration (number, location, and active thrusters). Results are presented from the implementation of a reconfigurable control allocation algorithm on the SPHERES (Synchronized Position Hold Engage Reorient Experimental Satellites) testbed aboard the International Space Station. Results demonstrate controllability for configurations with large center of mass shifts, varying number of thrusters, as well as maintaining performance from the baseline non-reconfigurable control allocation algorithm on SPHERES.
After 11 months of successful operation onboard the ISS US laboratory Destiny, the air quality monitors ANITA (Analyzing Interferometer for Ambient Air) was brought back to Earth on STS126 (ULF2). ANITA is a technology demonstrator flight experiment for continuous air quality monitoring inside the crewed cabin of the ISS with low detection limits and high time resolution. For the first time, the dynamics of the detected trace gas concentrations could be directly resolved by ANITA and correlated to gas events in the cabin. The system is the result of a long term ESA technology development programme initiated more than seventeen years ago. The ANITA mission was a cooperative project between ESA and NASA. ESA's responsibilities were the provision of the H/W, the data acquisition and the data evaluation. NASA was responsible for the launch, accommodation and operation onboard ISS, data download and the transportation of ANITA back to the Earth. ANITA was calibrated to detect and quantify 30 trace gases simultaneously with down to sub-ppm (parts per million) detection limits in addition to the always present background gases carbon dioxide and water vapour. The results of the mission are summarised in [ 1 ]. Further, with a specially developed gas bag hand pump system also gas analyses were performed on air samples from Node 1 of the Space Station. ANITA is a precursor for a permanent continuous trace gas monitoring system ANITA2 for ISS and future space vehicles. At the time of the conference the follow-on study on ANITA2 will have been initiated. This paper describes the measurement system, the lessons learned during the mission on ISS, and the planned follow-on activities. The work described has been performed under contract of the European Space Agency.
After the launch to the International Space Station with The Space Shuttle flight STS 118 13A.1 on August 9th 2007 and the accommodation in the US lab Destiny, the air quality monitor ANITA (Analyzing Interferometer for Ambient Air) has been successfully put into operation. ANITA is a technology demonstrator flight experiment being able to continuously monitor with high time resolution the air conditions within the crewed cabins of the ISS (International Space Station). The system has its origin in a long term ESA (European Space Agency) technology development program. The ANITA mission itself is an ESA-NASA cooperative project. ESA is responsible for the provision of the HW (Hardware), the data acquisition and data evaluation. NASA's responsibilities are launch, accommodation in the US Lab Destiny, operation and data download. The ANITA air analyser is designed to detect and quantify online and with high time resolution 30 trace gases simultaneously with down to sub-ppm (parts per million) detection limits in addition to the always present background gases carbon dioxide and water vapour. The air analyser thus monitors the trace gas dynamics of the spacecraft's atmosphere in providing continuous air monitoring as well as crew warning capability in case of malfunctions. Beside continuous measurements in the vicinity of the gas monitor, air samples from remote places in the International Space Station can be analyzed using gas bags and a hand pump. However, considering the experimental character of ANITA, the measurements are not on-line visible to the Crew. ANITA is an on-orbit test experiment and a precursor for a permanent continuous trace gas monitoring system on the ISS – ANITA II. It further represents a precursor system for future air monitoring in crewed vehicles being developed for the Human Space Exploration program. This is the first paper of two describing the measurement principle, the HW and the mission on the ISS. Finally, an outlook into the future highlights the potential of the ANITA technology for the Exploration program. The work described has been performed under contract of the European Space Agency.
Mold species in dust from the International Space Station identified and quantified by mold-specific quantitative PCR
Dust was collected over a period of several weeks in 2007 from HEPA filters in the U.S. Laboratory Module of the International Space Station (ISS). The dust was returned on the Space Shuttle Atlantis, mixed, sieved and the DNA was extracted. Using a DNA-based method called mold-specific quantitative PCR (MSQPCR), 39 molds were measured in the dust. Potential opportunistic pathogens Aspergillus flavus and Aspergillus niger and potential moderate toxin producers Penicillium chrysogenum and Penicillium brevicompactum were noteworthy. No cells of the potential opportunistic pathogens Aspergillus fumigatus, Aspergillus terreus, Fusarium solani or Candida albicans were detected.
Reentry Breakup Recorder: An innovative device for collecting data during breakup of reentering objects
More than 40 large, human-made, uncontrolled objects reenter the earth's atmosphere every year, and some fraction of the mass of each object survives to impact the ground or water. Some of these surviving objects are sizable and potentially hazardous. Recognizing this fact, space agencies are developing regulations and standards to limit ground hazards. Unfortunately, detailed information on how objects respond to the severe heating and loads environment is not available due to the difficulty in recording and broadcasting data during reentry and breakup. The Reentry Breakup Recorder (REBR) was developed using a different paradigm – rather than broadcasting data during the breakup event, record the data and broadcast it after the reentry has effectively ended, but before the data recorder actually impacts the Earth's surface. The paper describes how this approach minimizes the weight of the recording device and the overall cost of data recovery. The first flight tests of the REBR device were conducted in 2011; a REBR was inside the Japanese HTV2 and the European ATV-2 vehicles when they were deorbited into the Pacific Ocean. The paper presents a summary of the results of those tests and gives an overview of how future versions of REBR will revolutionize our understanding of reentry breakup and might be used to prototype "black box" systems for space transportation vehicles.
A swing bed canister assembly for a regenerative carbon dioxide removal system includes a housing that includes an integrally formed central wall that divides an adsorbing amine bed from a desorbing amine bed. The central wall defines spaces for each of the amine beds so that each portion of the desorbing amine bed is disposed in thermal communication with an adsorbing amine bed to facilitate desorption.
The ISS and the prior station Mir provided the proving ground for future human long-duration space activity. A recent European Space Agency study recommended “Measurement campaigns on the ISS form the ideal tool for experimental validation of radiation environment models, of transport code algorithms and reaction cross sections”. Indeed, prior measurements on Shuttle have provided vital information impacting both transport code and environmental model development. Recent studies using the ISS 7A configuration with TLD area monitors demonstrated that computational dosimetry requires environmental models with accurate anisotropic and dynamic behavior, detailed information on rack loading, and an accurate 6 degree-of-freedom description of the ISS trajectory. The ISS model is now configured for 11A and uses an anisotropic and dynamic geomagnetic transmission and trapped proton models. The ISS 11A is instrumented with both passive and active dosimetric devices. Time resolved measurements have the advantage of isolating trapped proton and galactic cosmic ray components as was essential to transport code validation in Shuttle data analysis. ISS 11A model validation will begin with passive dosimetry as was used with ISS 7A. Directional dependent active measurements will play an important role in the validation of environmental model anisotropies.