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NASA NTRS2012

Cargo Commercial Orbital Transportation Services Environmental Control and Life Support Integration

The International Space Station s (ISS) largest crew and cargo resupply vehicle, the Space Shuttle, retired in 2011. To help augment ISS resupply and return capability, NASA announced a project to promote the development of Commercial Orbital Transportation Services (COTS) for the ISS in January of 2006. By December of 2008, NASA entered into space act agreements with SpaceX and Orbital Sciences Corporation for COTS development and ISS Commercial Resupply Services (CRS). The intent of CRS is to fly multiple resupply missions each year to ISS with SpaceX s Dragon vehicle providing resupply and return capabilities and Orbital Science Corporation s Cygnus vehicle providing resupply capability to ISS. The ISS program launched an integration effort to ensure that these new commercial vehicles met the requirements of the ISS vehicle and ISS program needs. The Environmental Control and Life Support System (ECLSS) requirements cover basic cargo vehicle needs including maintaining atmosphere, providing atmosphere circulation, and fire detection and suppression. The ISS-COTS integration effort brought unique challenges combining NASA s established processes and design knowledge with the commercial companies new initiatives and limited experience with human space flight. This paper will discuss the ISS ECLS COTS integration effort including challenges, successes, and lessons learned.

Duchesne, Stephanie↗

NASA NTRS2016

Expanding NASA and Roscosmos Scientific Collaboration on the International Space Station

The International Space Station (ISS) is a world-class laboratory orbiting in space. NASA and Roscosmos have developed a strong relationship through the ISS Program Partnership, working together and with the other ISS Partners for more than twenty years. Since 2013, based on a framework agreement between the Program Managers, NASA and Roscosmos are building a joint program of collaborative research on ISS. This international collaboration is developed and implemented in phases. Initially, members of the ISS Program Science Forum from NASA and TsNIIMash (representing Roscosmos) identified the first set of NASA experiments that could be implemented in the "near term". The experiments represented the research categories of Technology Demonstration, Microbiology, and Education. Through these experiments, the teams from the "program" and "operations" communities learned to work together to identify collaboration opportunities, establish agreements, and jointly plan and execute the experiments. The first joint scientific activity on ISS occurred in January 2014, and implementation of these joint experiments continues through present ISS operations. NASA and TsNIIMash have proceeded to develop "medium term" collaborations, where scientists join together to improve already-proposed experiments. A major success is the joint One-Year Mission on ISS, with astronaut Scott Kelly and cosmonaut Mikhail Kornienko, who returned from ISS in March, 2016. The teams from the NASA Human Research Program and the RAS Institute for Biomedical Problems built on their considerable experience to design joint experiments, learn to work with each other's protocols and processes, and share medical and research data. New collaborations are being developed between American and Russian scientists in complex fluids, robotics, rodent research and space biology, and additional human research. Collaborations are also being developed in Earth Remote Sensing, where scientists will share data from imaging systems mounted on ISS as well as other orbiting spacecraft to improve our understanding of the Earth and its climate. NASA and Roscosmos continue to encourage international scientific cooperation and expanded use of the ISS Laboratory. "Long-term", larger collaborations will achieve scientific objectives that no single national science team or agency can achieve on its own. The joint accomplishments achieved so far have paved the way for a stronger international scientific community and improved results and benefits from ISS.

Hasbrook, Pete↗

NASA NTRS2006

Generalized Separation of an Object Jettisoned from the ISS

The International Space Station (ISS) Program faces unprecedented logistics challenges in both upmass and downmass. Some items employed on the ISS exterior present significant technical issues for a controlled de-orbit on either the shuttle or an expendable supply vehicle. Such manifest problems arise due to structural degradation, insufficient containment of hazardous pressures or contents, excessive size, or some combination of all of these factors. In addition, the mounting hardware and other flight service equipment to manifest the returned equipment must itself be launched, competing with other upmass. EVA techniques and equipment to successfully contain and secure such problematic equipment result in numerous significant risks to the spacewalking crews and cost and schedule risks to the program. The ISS Program office has therefore developed a policy that advises the jettison of the most problematic objects. Such jettisoned items join a small family of nearly co-planar orbital debris objects that threaten the ISS on several timescales, besides threatening all satellites with perigee below the ISS orbit and the general human population on Earth. This analysis addresses the governing physics and the ensuing risks when an object is jettisoned. It is shown that there are four time domains which must be considered, each with its own inherent problems, and that a ballistic solution is usually possible that satsfies all constraints in all domains.

Bacon, Jack↗

NASA NTRS2010

Proposal for Ground Safety Review Coordination at ISS Launch Sites

As the transportation of ISS payloads and cargo shifts from KSC to other launch sites, close coordination of ground safety review processes would be of benefit to all parties. The benefit would have the launch sites receiving consistent data that would require less effort to review while still meeting their needs. Until recently, ground safety focus for the ISS program has been almost exclusively for prelaunch processing at KSC/post-landing processing at KSC/DFRC Each launch site, used by the ISS Program, has a ground safety review process. Ground safety viewed as local prerogative. Up till now, ground processing has consisted of low risk/low hazard items; but this will not always be the case. Recent coordination issues associated with the ground safety review of ORU's to be processed at Tanegashima for HTV-2, illustrate that IP ground safety review processes are not well understood by the ISS community at large. Confusion for data providers (US only?). Lack of internal review process for data being submitted to launch sites can lead to inconsistent submittals. NCRs/HRs. Majority of IP ground safety requirements are based upon old KHB 1700.7 (now KNPR 8715.3, Chapter 20). Proposals include: Establish a ground safety working group as part of the MS&MAP. Search for efficiencies in requirements and data submittal processes. Document processes in NSTS 13830/SSP 30599. Each launch site report out its payload ground safety status at the F2F (Monthly's as required). Completions/due dates/NCRs/issues/changes. Establish internal processes for review of ground safety submittals.

Kirkpatrick, Paul D.↗

NASA NTRS2006

Habitability and Human Factors: Lessons Learned in Long Duration Space Flight

This study documents the investigation of qualitative habitability and human factors feedback provided by scientists, engineers, and crewmembers on lessons learned from the ISS Program. A thorough review and understanding of this data is critical in charting NASA's future path in space exploration. NASA has been involved in ensuring that the needs of crewmembers to live and work safely and effectively in space have been met throughout the ISS Program. Human factors and habitability data has been collected from every U.S. crewmember that has resided on the ISS. The knowledge gained from both the developers and inhabitants of the ISS have provided a significant resource of information for NASA and will be used in future space exploration. The recurring issues have been tracked and documented; the top 5 most critical issues have been identified from this data. The top 5 identified problems were: excessive onsrbit stowage; environment; communication; procedures; and inadequate design of systems and equipment. Lessons learned from these issues will be used to aid in future improvements and developments to the space program. Full analysis of the habitability and human factors data has led to the following recommendations. It is critical for human factors to be involved early in the design of space vehicles and hardware. Human factors requirements need to be readdressed and redefined given the knowledge gained during previous ISS and long-duration space flight programs. These requirements must be integrated into vehicle and hardware technical documentation and consistently enforced. Lastly, space vehicles and hardware must be designed with primary focus on the user/operator to successfully complete missions and maintain a safe working environment. Implementation of these lessons learned will significantly improve NASA's likelihood of success in future space endeavors.

Baggerman, Susan D.↗

NASA NTRS2014

Quantitative Risk Modeling of Fire on the International Space Station

The International Space Station (ISS) Program has worked to prevent fire events and to mitigate their impacts should they occur. Hardware is designed to reduce sources of ignition, oxygen systems are designed to control leaking, flammable materials are prevented from flying to ISS whenever possible, the crew is trained in fire response, and fire response equipment improvements are sought out and funded. Fire prevention and mitigation are a top ISS Program priority - however, programmatic resources are limited; thus, risk trades are made to ensure an adequate level of safety is maintained onboard the ISS. In support of these risk trades, the ISS Probabilistic Risk Assessment (PRA) team has modeled the likelihood of fire occurring in the ISS pressurized cabin, a phenomenological event that has never before been probabilistically modeled in a microgravity environment. This paper will discuss the genesis of the ISS PRA fire model, its enhancement in collaboration with fire experts, and the results which have informed ISS programmatic decisions and will continue to be used throughout the life of the program.

Castillo, Theresa↗

NASA NTRS2016

Integrating MBSE into Ongoing Projects: Requirements Validation and Test Planning for the ISS SAFER

The International Space Station (ISS) Simplified Aid for Extra Vehicular Activity (EVA) Rescue (SAFER) is the spacewalking astronaut's final safety measure against separating from the ISS and being unable to return safely. Since the late 1990s, the SAFER has been a standard element of the spacewalking astronaut's equipment. The ISS SAFER project was chartered to develop a new block of SAFER units using a highly similar design to the legacy SAFER (known as the USA SAFER). An on-orbit test module was also included in the project to enable periodic maintenance/propulsion system checkout on the ISS SAFER. On the ISS SAFER project, model-based systems engineering (MBSE) was not the initial systems engineering (SE) approach, given the volume of heritage systems engineering and integration (SE&I) products. The initial emphasis was ensuring traceability to ISS program standards as well as to legacy USA SAFER requirements. The requirements management capabilities of the Cradle systems engineering tool were to be utilized to that end. During development, however, MBSE approaches were applied selectively to address specific challenges in requirements validation and test and verification (T&V) planning, which provided measurable efficiencies to the project. From an MBSE perspective, ISS SAFER development presented a challenge and an opportunity. Addressing the challenge first, the project was tasked to use the original USA SAFER operational and design requirements baseline, with a number of additional ISS program requirements to address evolving certification expectations for systems operating on the ISS. Additionally, a need to redesign the ISS SAFER avionics architecture resulted in a set of changes to the design requirements baseline. Finally, the project added an entirely new functionality for on-orbit maintenance. After initial requirements integration, the system requirements count was approaching 1000, which represented a growth of 4x over the original USA SAFER system. This presented the challenge - How to confirm that this new set of requirements set would result in the creation of the desired capability.

Anderson, Herbert A.↗

NASA NTRS2018

The SPACE Computer Code for Analyzing the International Space Station Electrical Power System: Past, Present, and Future

The System Power Analysis for Capability Evaluation (SPACE) computer code was initially developed by NASA in 1988 to assess the Space Station Freedom electric power system and later adapted to support contractor electrical power system capability analyses for the International Space Station (ISS). Over time, the code has supported many efforts such as ISS redesign activities in the early 1990s, assessment of time-phased loads against power system operating limits for future ISS assembly flights (including Certification of Flight Readiness reviews by the ISS program office), and determining the optimum solar array gimbal positions while respecting keep-out zones which minimize both solar array contamination and structural loads. The code has been validated by comparisons with ISS on-orbit data in multiple validation episodes. Recent updates to the code include the incorporation of a Lithium-Ion battery model in addition to the Nickel Hydrogen battery model and modifications to the solar array degradation model to better match on-orbit test results. SPACE has also been extended beyond the ISS to include modeling of the Orion Multi-Purpose Crew Vehicle electrical power system (SPACE-MPCV) and Mars Surface Electrical Power Systems (MSEPS). Portions of SPACE were integrated with a trajectory code to form a Solar Electric Propulsion Simulation (SEPSim), which can be used for analyzing solar electric propulsion missions. In addition, SPACE methods and subroutines have been adapted to a multitude of other projects. This paper summarizes the initial code development and subsequent code utilization in the context of the overall ISS program development and on-orbit operations. Recent updates and results from the code are discussed, including preliminary analyses for the Orion power system.

Electrical Power System↗

NASA NTRS2009

Modification of the International Space Station USOS to Support Installation and Activation of the Node 3 Element

The International Space Station (ISS) program is nearing an assembly complete configuration with the addition of the final resource node module in early 2010. The Node 3 module will provide critical functionality in support of permanent long duration crews aboard ISS. The new module will permanently house the regenerative Environment Control and Life Support Systems (ECLSS) and will also provide important habitability functions such as waste management and exercise facilities. The ISS program has selected the Port side of the Node 1 "Unity" module as the permanent location for Node 3 which will necessitate architecture changes to provide the required interfaces. The USOS ECLSS fluid and ventilation systems, Internal Thermal Control Systems, and Avionics Systems require significant modifications in order to support Node 3 interfaces at the Node 1 Port location since it was not initially designed for that configuration. This paper outlines the design, development, certification, and implementation of these changes in support of ISS assembly complete.

Link, Dwight E., Jr.↗

NASA NTRS2011

International Space Station Utilization: Tracking Investigations from Objectives to Results

Since the first module was assembled on the International Space Station (ISS), on-orbit investigations have been underway across all scientific disciplines. The facilities dedicated to research on ISS have supported over 1100 investigations from over 900 scientists representing over 60 countries. Relatively few of these investigations are tracked through the traditional NASA grants monitoring process and with ISS National Laboratory use growing, the ISS Program Scientist s Office has been tasked with tracking all ISS investigations from objectives to results. Detailed information regarding each investigation is now collected once, at the first point it is proposed for flight, and is kept in an online database that serves as a single source of information on the core objectives of each investigation. Different fields are used to provide the appropriate level of detail for research planning, astronaut training, and public communications. http://www.nasa.gov/iss-science/. With each successive year, publications of ISS scientific results, which are used to measure success of the research program, have shown steady increases in all scientific research areas on the ISS. Accurately identifying, collecting, and assessing the research results publications is a challenge and a priority for the ISS research program, and we will discuss the approaches that the ISS Program Science Office employs to meet this challenge. We will also address the online resources available to support outreach and communication of ISS research to the public. Keywords: International Space Station, Database, Tracking, Methods

Ruttley, T. M.↗

NASA NTRS2026

Outgassing Characterization of Common Trash Items for Disposal By Nanoracks Airlock on the International Space Station

The arrival of the Nanoracks Airlock to the International Space Station (ISS) has provided the ISS program the capability to dispose of common trash items. The concept of operations involved the crew bagging up those items into a trash bag and then utilizing the robotic arm and the airlock to jettison the trash bag. Because of the unknown thermal vacuum stability of some of the items, a molecular contamination concern was raised by the ISS program as the trash is exposed to vacuum upon the evacuation of air from the airlock and the robotic arm moving the airlock to its jettison location. In order to characterize the representative outgassing rates for ISS trash, thermal vacuum testing was performed at White Sands Test Facility. Trash was sorted into a “lower” outgassing bag and a “mixed” bag. The “mixed” trash bag contained more items that were suspected to be not vacuum stable. Load cells were chosen as the primary means for measuring mass loss. A sharp decay in the outgassing rate was observed in the first 30 minutes followed by a slower decay. As expected, the “mixed” bag lost more mass. While Quartz Crystal Microbalances (QCMs) are often utilized to measure long term outgassing rates and the sticking coefficients of contaminants at different operating temperatures for vacuum stable materials, these measurements proved difficult due to the amount and the inclusion of materials with suspect thermal vacuum stability. Because of high rates of material outgassing, the facility was unable to maintain the CQCM temperature setpoint of 80 K QCMs.. The QCMs operating at the warmer temperatures also saturated on occasion due to high levels of condensed matter. Though testing was able to confirm high risk of outgassing contamination for the program, true sticking coefficients could not be determined, available measurements are provided herein.

Alvin Y Huang↗

NASA NTRS1996

International Space Station ECLSS Technical Task Agreement Summary Report

A summary of work accomplished under Technical Task Agreement by the Marshall Space Flight Center (MSFC) documents activities regarding the Environmental Control and Life Support Systems (ECLSS) of the International Space Station (ISS) program. These MSFC activities were in-line to the designing, the development, the testing, and the flight of ECLSS equipment. MSFC's unique capabilities for performing integrated system testing and analyses, and its ability to perform some tasks cheaper and faster to support ISS program needs are the basis for the Technical Task Agreement activities. Tasks were completed in the Water Recovery Systems, Air Revitalization Systems, and microbiology areas. The results of each task is described in this summary report.

Minton-Summers, S.↗

NASA NTRS2004

Assessment and Control of Spacecraft Charging Risks on the International Space Station

The International Space Station (ISS) operates in the F2 region of Earth's ionosphere, orbiting at altitudes ranging from 350 to 450 km at an inclination of 51.6 degrees. The relatively dense, cool F2 ionospheric plasma suppresses surface charging processes much of the time, and the flux of relativistic electrons is low enough to preclude deep dielectric charging processes. The most important spacecraft charging processes in the ISS orbital environment are: 1) ISS electrical power system interactions with the F2 plasma, 2) magnetic induction processes resulting from flight through the geomagnetic field and, 3) charging processes that result from interaction with auroral electrons at high latitude. Recently, the continuing review and evaluation of putative ISS charging hazards required by the ISS Program Office revealed that ISS charging could produce an electrical shock hazard to the ISS crew during extravehicular activity (EVA). ISS charging risks are being evaluated in an ongoing measurement and analysis campaign. The results of ISS charging measurements are combined with a recently developed model of ISS charging (the Plasma Interaction Model) and an exhaustive analysis of historical ionospheric variability data (ISS Ionospheric Specification) to evaluate ISS charging risks using Probabilistic Risk Assessment (PRA) methods. The PRA combines estimates of the frequency of occurrence and severity of the charging hazards with estimates of the reliability of various hazard controls systems, as required by NASA s safety and risk management programs, to enable design and selection of a hazard control approach that minimizes overall programmatic and personnel risk. The PRA provides a quantitative methodology for incorporating the results of the ISS charging measurement and analysis campaigns into the necessary hazard reports, EVA procedures, and ISS flight rules required for operating ISS in a safe and productive manner.

Koontz, Steve↗

NASA NTRS2000

STS-92 Preflight Briefings Video Feed and International Space Station Overview

The first half of this video is a collection of video feeds from various preflight conferences and simulations show the payload bay and payload equipment. The International Space Station's (ISS) structure is seen, as are close-up shots of the Z-1 truss. Footage shows extravehicular activity (EVA) underwater training. The second half of the video is a preflight conference on the mission objectives concerning the ISS. Tommy Halloway, Manager, ISS Program, and Robert Cabana, ISS Manager for International Operations, discuss the STS-92 mission in terms of the ISS and the role of ISS in the future. Mr. Cabana gives the status of present and future ISS hardware. The men then answer questions from the press.

Source record↗

NASA NTRS2003

Assessment and Control of Spacecraft Charging Risks on the International Space Station

Electrical interactions between the F2 region ionospheric plasma and the 160V photovoltaic (PV) electrical power system on the International Space Station (ISS) can produce floating potentials (FP) on the ISS conducting structure of greater magnitude than are usually observed on spacecraft in low-Earth orbit. Flight through the geomagnetic field also causes magnetic induction charging of ISS conducting structure. Charging processes resulting from interaction of ISS with auroral electrons may also contribute to charging albeit rarely. The magnitude and frequency of occurrence of possibly hazardous charging events depends on the ISS assembly stage (six more 160V PV arrays will be added to ISS), ISS flight configuration, ISS position (latitude and longitude), and the natural variability in the ionospheric flight environment. At present, ISS is equipped with two plasma contactors designed to control ISS FP to within 40 volts of the ambient F2 plasma. The negative-polarity grounding scheme utilized in the ISS 160V power system leads, naturally, to negative values of ISS FP. A negative ISS structural FP leads to application of electrostatic fields across the dielectrics that separate conducting structure from the ambient F2 plasma, thereby enabling dielectric breakdown and arcing. Degradation of some thermal control coatings and noise in electrical systems can result. Continued review and evaluation of the putative charging hazards, as required by the ISS Program Office, revealed that ISS charging could produce a risk of electric shock to the ISS crew during extra vehicular activity. ISS charging risks are being evaluated in ongoing ISS charging measurements and analysis campaigns. The results of ISS charging measurements are combined with a recently developed detailed model of the ISS charging process and an extensive analysis of historical ionospheric variability data, to assess ISS charging risks using Probabilistic Risk Assessment (PRA) methods. The PRA analysis (estimated frequency of occurrence and severity of the charging hazards) are then used to select the hazard control strategy that provides the best overall safety and mission success environment for ISS and the ISS crew. This paper presents: 1) a summary of ISS spacecraft charging analysis, measurements, observations made to date, 2) plans for future ISS spacecraft charging measurement campaigns, and 3) a detailed discussion of the PRA strategy used to assess ISS spacecraft charging risks and select charging hazard control strategies

Koontz, Steve↗

NASA NTRS2010

GRC Ground Support Facilities

The ISS Program is conducting an "ISS Research Academy' at JSC the first week of August 2010. This Academy will be a tutorial for new Users of the International Space Station, focused primarily on the new ISS National Laboratory and its members including Non-Profit Organizations, other government agencies and commercial users. Presentations on the on-orbit research facilities accommodations and capabilities will be made, as well as ground based hardware development, integration and test facilities and capabilities. This presentation describes the GRC Hardware development, test and laboratory facilities.

SaintOnge, Thomas H.↗

NASA NTRS2018

Evaluation of Crew-Centric Onboard Mission Operations Planning and Execution Tool: Year 2

Currently, mission planning for the International Space Station (ISS) is largely affected by ground operators in mission control. The task of creating a week-long mission plan for ISS crew takes dozens of people multiple days to complete, and is often created far in advance of its execution. As such, re-planning or adapting to changing real-time constraints or emergent issues is similarly taxing. As we design for future mission operations concepts to other planets or areas with limited connectivity to Earth, more of these ground-based tasks will need to be handled autonomously by the crew onboard.There is a need for a highly usable (including low training time) tool that enables efficient self-scheduling and execution within a single package. The ISS Program has identified Playbook as a potential option. It already has high crew acceptance as a plan viewer from previous analogs and can now support a crew self-scheduling assessment on ISS or on another mission. The goals of this work, a collaboration between the Human Research Program and the ISS Program, are to inform the design of systems for more autonomous crew operations and provide a platform for research on crew autonomy for future deep space missions. Our second year of the research effort have included new insights on the crew self-scheduling sessions performed by the crew through use on the HERA (Human Exploration Research Analog) and NEEMO (NASA Extreme Environment Mission Operations) analogs. Use on the NEEMO analog involved two self-scheduling strategies where the crew planned and executed two days of EVAs (Extra-Vehicular Activities). On HERA year two represented the first HERA campaign where we were able to perform research tasks. This involved selected flexible activities that the crew could schedule, mock timelines where the crew completed more complex planning exercises, usability evaluation of the crew self-scheduling features, and more insights into the limit of plan complexity that the crew could effectively self-schedule. In parallel we have added in new features and functionality in the Playbook tool based off of our insights from crew self-scheduling in the NASA analogs. In particular this year we have added in the ability for the crew to add, edit, and remove their own activities in the Playbook tool, expanding the type of planning and re-planning possible in the tool and opening up the ability for more free form plan creation. The ability to group and manipulate groups of activities from the plan task list was also added, allowing crew members to add predefined sets of activities onto their mission timeline. In addition we also added a way for crew members to roll back changes in their plan, in order to allow an undo like capability. These features expand and complement the initial self-scheduling features added in year one with the goal of making crew autonomous planning more efficient. As part of this work we have also finished developing the first version of our Playbook Data Analysis Tool, a research tool built to interpret and analyze the unobtrusively collected data obtained during the NASA analog missions through Playbook. This data which includes user click interaction as well as plan change information, through the Playbook Data Analysis Tool, allows us to playback this information as if a video camera was mounted over the crewmember's tablet. While the primary purpose of this tool is to allow usability analysis of crew self-scheduling sessions used on the NASA analog, since the data collected is structured, the tool can automatically derive metrics that would be traditionally tedious to achieve without manual analysis of video playback. We will demonstrate and discuss the ability for future derived metrics to be added to the tool. In addition to the current data and results gathered in year two we will also discuss the preparation and goals of our International Space Station (ISS) onboard technology demonstration with Playbook. This technology demonstration will be preformed as part of the CAST payload starting in late 2016.

onboard planning↗

NASA NTRS2002

Lessons Learned In Developing Multiple Distributed Planning Systems for the International Space Station

The planning processes for the International Space Station (ISS) Program are quite complex. Detailed mission planning for ISS on-orbit operations is a distributed function. Pieces of the on-orbit plan are developed by multiple planning organizations, located around the world, based on their respective expertise and responsibilities. The "pieces" are then integrated to yield the final detailed plan that will be executed onboard the ISS. Previous space programs have not distributed the planning and scheduling functions to this extent. Major ISS planning organizations are currently located in the United States (at both the NASA Johnson Space Center (JSC) and NASA Marshall Space Flight Center (MSFC)), in Russia, in Europe, and in Japan. Software systems have been developed by each of these planning organizations to support their assigned planning and scheduling functions. Although there is some cooperative development and sharing of key software components, each planning system has been tailored to meet the unique requirements and operational environment of the facility in which it operates. However, all the systems must operate in a coordinated fashion in order to effectively and efficiently produce a single integrated plan of ISS operations, in accordance with the established planning processes. This paper addresses lessons learned during the development of these multiple distributed planning systems, from the perspective of the developer of one of the software systems. The lessons focus on the coordination required to allow the multiple systems to operate together, rather than on the problems associated with the development of any particular system. Included in the paper is a discussion of typical problems faced during the development and coordination process, such as incompatible development schedules, difficulties in defining system interfaces, technical coordination and funding for shared tools, continually evolving planning concepts/requirements, programmatic and budget issues, and external influences. Techniques that mitigated some of these problems will also be addressed, along with recommendations for any future programs involving the development of multiple planning and scheduling systems. Many of these lessons learned are not unique to the area of planning and scheduling systems, so may be applied to other distributed ground systems that must operate in concert to successfully support space mission operations.

Maxwell, Theresa G.↗