ABSTRACT. The International Space Station (ISS) will provide investigators around the world a long-duration space science and technology research capability. This diverse ISS utilization activity will be supported by geographically-distributed operations centers in participating partner nations. NASA will integrate and coordinate ISS utilization through a Payload Operations Integration Center (POIC) at Marshall Space Flight Center. The POIC will work with the partner operations centers to coordinate and integrate Station operations functions. The concept for integrating ISS payload operations are described herein.

The payload activity planning function results in summary plans and detailed timelines. Partners and payload users are responsible for planning their respective payload activities. POIC planners, working with other operations centers, integrate these plans and timelines.

The payload operations control function supports the execution of the timelines. POIC personnel monitor the execution of ISS crew and ground-based payload user scheduled activities. They coordinate timeline changes to avoid activity conflicts. POIC communications, telemetry, and command processing systems are used to perform payload operations control functions.

The payload data management function coordinates video, science, and housekeeping telemetry collection and distribution. The POIC data management team coordinates payload utilization of onboard data systems, the Tracking and Data Relay Satellite (TDRS) system, and ground communications and data processing and routing systems.

Finally, the POIC is the operations hub of ISS utilization. By interfacing with the other ISS centers using information management and communications systems, the POIC personnel facilitate routine information dissemination and coordination. The POIC facility provides communications, information, and planning systems to perform these tasks.

The International Space Station (ISS) will provide investigators around the world a long-duration space science and technology research capability. The ISS will provide unique capabilities for the crew to conduct experiments onboard the Station using payload hardware in pressurized laboratories and hardware mounted externally and exposed to space. The investigators will also be provided with remote control capabilities for tele-operations1. A wide range of research is anticipated, including life sciences, materials studies, earth observations, atmospheric physics, and astronomy.

This diverse ISS utilization activity will be supported by geographically-distributed operations centers in participating partner nations (see table 1). Geographical distribution of mission operations has been demonstrated on Space Shuttle and Spacelab2 missions. Europe has pursued the approach of geographically distributing its payload operations support infrastructure3. Other ISS partners, including the USA, are planning to support additional user operations facilities and telescience support centers associated with the payloads they are sponsoring (see table 2). This experience -- and the ISS operations concept -- require overall payload operations integration to achieve a unified operation.

Table 1. Geographically-distributed payload operations centers in ISS partner nations.

ISS Partner	Payload Operations Center	Location
USA	Payload Operations Integration Center	Huntsville, Alabama USA
Russia	Mission Control Center - Moscow	Moscow, Russia
Canada	User Support Operations Center (USOC)	Huntsville, Alabama, USA
Japan	Space Station Integration and Promotion Center (SSIPC)	Tsukuba, Japan
ESA	Attached Pressurized Module Control Center	Europe

The ISS partners have agreed that NASA will integrate and coordinate ISS utilization through a Payload Operations Integration Center (POIC) at Marshall Space Flight Center in Huntsville, Alabama USA⁴. Payload operations functions include ISS payload activity planning, payload operations control, payload data management, and overall payload operations integration. All of the partners' operations centers perform these functions, but they must be integrated to ensure the safety of the crew and non-interference of concurrent payload and Station systems operations. The POIC will orchestrate these functions.

The distributed payload operations concepts have been defined and encompass these functions5,6. The integration and orchestration of tasks to be performed by the POIC are described by function as follows.

The payload activity planning function results in summary plans and detailed timelines. POIC planners working with other operations centers generate these integrated plans and timelines. The payload planning process5 starts with resource distribution according to multilateral agreements defined in tactical-level ISS plans. The POIC leads the execution-level planning activities performed by all ISS partners and researchers. Key planning tasks are performed by the POIC to ensure generation of a coordinated, compatible timeline of payload activities: (1) The resources available for overall payload activities are defined by working with the Space Station Control Center (SSCC). (2) The payload resources are divided according to the distribution agreements and the requirements provided by the researchers and integrated by the partner planning centers. (3) Payload planning constraints are provided to the partners to assure safety and operations compatibility. (4) Timelines are provided to the POIC by each partner planning center and are checked automatically by the planning system and integrated into single timeline of activities.

The payload operations control function is associated with timeline execution. Under normal circumstances, the ISS crew on the Station and investigators at geographically-dispersed locations perform the primary execution activities. POIC personnel monitor the execution of ISS crew and ground-based payload user activities for consistency with the timeline. If an event occurs which affects other scheduled activities adversely, the POIC coordinates the conflict's resolution. This includes coordinating changes to the timeline, procedures, support systems configurations, etc. Change implementation is the responsibility of the operations center that produces and maintains the operations product.

Effective payload operations requires direct conversation between the ISS crew, the POIC and the partner operations centers -- and in some cases -- the research scientists. On a scheduled basis, the POIC coordinates and enables these crew conversations. The POIC is the crew's primary interface for overall payload operations. The POIC coordinates any payload-related messages between the crew and the payload operations community on the ground.

Partners and payload users develop and collect crew payload operations procedures into operations data files. They also maintain these payload procedures and files. When procedure changes are required, the POIC ensures they are coordinated with the crew. The POIC also ensures that the procedures satisfy the safety requirements and do not interfere with other operations. A common format standard for procedures is planned for all procedures, and the partners and procedure developers may consult with the POIC on compliance with the standard.

The POIC also assists the crew and ground personnel with tracking the stowage locations of payload items. The utilization of shared payload consumables (e.g., tissues, microscope slides, video cassettes, etc.) are tracked by the POIC. The POIC maintains and provides this information to the payload operations community electronically.

Tele-operation of payloads is also performed by the geographically-dispersed payload operations centers. Payloads are controlled from the ground according to the timeline. Also, if an unexpected event occurs, payload users may send unscheduled commands to their payload. The POIC coordinates all payload command and file transmissions to the Station.

The payload data management function coordinates video, science, and housekeeping telemetry collection and distribution. The POIC data management team coordinates payload utilization of onboard data systems, Tracking and Data Relay Satellite, and ground communications and data systems.

The POIC plans and coordinates the onboard data systems configurations with the partner operations centers. The POIC performs the detailed operations of the payload data support systems provided in the U.S. elements while the partners perform similar tasks for their respective elements.

Payload video is collected and recorded or transmitted to the ground. Payload health and status sensor readings, as well as ancillary measurements of ISS systems and environmental conditions, are transmitted also.

After the telemetry is received, a Payload Data Services System (PDSS), co-located with the POIC, processes and routes the data to the users. The POIC directs these PDSS support activities. The POIC is the partners' principal interface for payload data management coordination.

The POIC will be the operations hub of ISS utilization. A continuous mission of space research in low earth orbit begins with the launch of the first payloads during ISS assembly. Daily payload operations will change and evolve by design -- and in to response to how events actually occur. Planned changes include crew rotations, additional Station modules, and new payloads. But the ISS crew and users will also respond to unanticipated supernova observations, solar flares, delayed launches of visiting Space Shuttle and Soyuz vehicles, and broken hardware. All of these events will require decisions regarding payload planning and operations that must be coordinated in two dimensions: (1) Over time and (2) Across the payload operations community.

The continuous operations environment and long-duration characteristics of the ISS utilization mission allow wider intervals of response times to changing events. By comparison, in a Space Shuttle mission of one or two weeks, most decisions in response to actual events must be made and implemented by the end of the flight. The ISS is designed for a continuos 15-year mission; therefore, a response to an event could be delayed for years. These decisions must be communicated to strategic-, tactical-, and execution-level planners, as well as to the teams implementing payload operations each week.

The overall payload operations integration function requires the POIC to collect information from the ISS partners and user community based on events, and to recommend and decide when and how to respond. The affected international investigators may choose to collaborate to make the most effective use of Station capabilities for their research. The POIC facilitates this collaboration by providing options for planning and executing the payload operations based on their collective research requirements. Any recommendations made by the investigators' group will be used to plan the payload operations within the capabilities and requirements of the ISS program.

The POIC communicates these integrated responses to the appropriate ISS planning groups, from strategic levels (with 5-year planning horizons), to tactical levels (with 2-year planning horizons), to the execution level (planning and preparing for activities within the next year). These are unique interfaces to organizations external to the control centers, but are part of the ISS program management teams. Figure 1 illustrates the communications interfaces required to support continuous ISS payload operations.

Figure 1. Continuous Payload Operations Communications

The ISS payload operations concept is based on distribution of payload operations responsibility to the researchers and ISS partners. The long-duration nature of the ISS mission dictates geographic distribution of payload operations activities, in the ISS partner nations' operations centers and near research facilities. Integration and coordination of payload operations will be a challenging task assigned to the POIC. Unified payload operations is the basic objective the POIC must achieve through communication and collaboration with the payload community.

1. S. R. Noneman, "Ground Tended Payload Operations of Space Station Freedom," IAF-92-0714, September 1992.

2. P. Hamby, "The ATLAS Series," AIAA-95-3683, September 1995.

3. T. Andersen, et al., "Concept of a European Wide Ground Infrastructure for Experimentation in the COLUMBUS Elements Attached Laboratory and Free Flyer," IAF-91-105, October 1991.

4. C. S. Griner and S. R. Noneman, "Space Station Freedom Payload Operations in the 21st Century," IAF-91-101, October 1991.

5. S. R. Noneman and T. W. Inman, "Space Station Payload Command And Control Distributed Operations," AIAA 95-3534, September 1995.

6. T. Maxwell and J. Hagopian, "An Approach for Implementing Distributed Planning for Space Station Payload Operations," AIAA-95-3538, September 1995.