The continuing effort of advancing sound and accepted spacecraft bus standards is the objective of the Office of the Secretary of Defense’s (OSD) Operationally Responsive Space (ORS) Bus Standards Initiative. This effort involves multiple government, industry, and academia participants assembled into an Integrated System Engineering Team (ISET). The initial release of the standards was presented at the 21 AIAA/USU Conference on Small Satellites as “ISET ORS Bus Standards and Prototype” and contains important background information. This paper updates the status of the ORS Bus Standards, including a major update to the software standards and data protocols. All of these standards are freely available for download from http://projects.nrl.navy.mil/standardbus/. This paper provides an update on the status of the prototype developed to support the TacSat-4 Mission is provided, as well as a report of other ORS standards implementation efforts. The first half of this paper reviews the process as discussed in previous papers. The second half of this paper describes the specific implementation of the bus prototype including design highlights and lessons learned. REVIEW OF PHASE III OBJECTIVES The first objective of the ORS Phase III Bus Standards effort has been to establish a national systems engineering working group with the US small satellite industry and academia to develop primary interface standards for a class of ORS spacecraft. The second objective has been to obtain consensus and buy-in by maturing the bus standards in an open environment with broad government, industry, and academia participation. Lastly, Phase III has intended to bridge the gap between Science and Technology (S&T) buses and an operational bus capability. The NRL and JHU/APL engineering team successfully designed and developed a prototype bus according to the ORS bus and interface standards. This prototype bus has completed environmental testing and acceptance testing and is now ready for payload integration and flight. Not all of the ORS standards have been validated through the first prototype build; however, critical elements such as mechanical, electrical, and software data interfaces between major space vehicle Jaffe 1 22 Annual AIAA/USU nd Conference on Small Satellites segments, including the payload to bus, launch vehicle to bus, and bus to payload data interfaces, were validated. Additionally, other parties have implemented or are in the process of implementing hardware and software to the latest ORS standards. ORS BUS STANDARDS DEVELOPMENT Since early 2005, several phases and efforts have shaped the development of the ORS standards. Over a dozen aerospace companies have participated substantively in the standards development, most as part of the ISET. The analysis from the Massachusetts Institute of Technology/Lincoln Laboratories (MIT/LL) Phase 1 effort was the starting point for the ISET in determining the proper balance between cost and performance of ORS/ spacecraft to be militarily useful. The MIT/LL report had several findings based strictly on the utility analyses: • A tactical spacecraft bus, standardized across a variety of National Security Space (NSS) missions, can meet many, but not all the needs of a tactical commander. • Small tactical satellites can achieve large increases in mission utility if used in constellations to improve persistence. • There exist standard performance specifications for a small tactical satellite bus that satisfy a wide range of NSS missions. Table 1 summarizes various performance characteristics for the type of spacecraft bus applicable to an ORS system. Each column presents the results for a single spacecraft and show that actual ORS spacecraft characteristics should not be less than presented or they will not be useful. Based on the study and a preliminary ISET deliberation session, the ISET adopted the following charter: "Generate a set of spacecraft bus standards, in sufficient detail to allow a space vehicle manufacturer to design, build, integrate, test and deliver a low cost spacecraft bus satisfying an enveloping set of mission requirements (launch vehicle, target orbit, payload, etc) in support of a tactical operational responsive space mission." From the charter, the ISET identified the following four objectives and goals to achieve in support of tactical ORS missions: • Develop Top Level Mission Requirements and Concept of Operations Envelope • Identify and Establish External Interface Standards for a Spacecraft Bus • Establish Functional and Performance Standards for a Spacecraft Bus • Establish Programmatic, Mission Assurance, and Quality Assurance Standards for Spacecraft Bus Procurement Table 1: ORS Bus Characteristics Phase I Study Once the goals and the charter of the ISET were established, a series of deliberation session were held, resulting in the preliminary version of the standards. The draft standards were released just prior to System Requirements Review in November 2005. The first revision of the standards was released in July 2006 in conjunction with the ORS Phase III Prototype Preliminary Design Review, and the second revision was released after the Critical Design Review in January 2007. Revision 2 focused on answering the TBRs and TBDs throughout the documents. Of particular note is the distinction that the ISET has made between “Bus Standards” and “Standard Bus.” These two terms are sometimes interchangeably used to refer to the ORS Phase III Effort interchangeably, this equivalency is incorrect, and the terms represent two distinct approaches. A “standard bus” designates a single spacecraft bus and configuration for all Jaffe 2 22 Annual AIAA/USU nd Conference on Small Satellites missions or mission classes, and the design must meet all stated requirements and specifications. This approach has been tried in the past and usually leads to a “least denominator approach, and an over designed system”. For the ORS Phase III effort, the goal has been to develop “bus standards,” which provide a set of requirements that can be used to satisfy a defined range of mission performance characteristics. These standards may be tailor-able/selectable for mission specific capability, and provide a framework for overall spacecraft design approach and philosophy. Furthermore, they provide procurement flexibility, which allows for a “family” of spacecraft, with individual members applicable to a defined performance envelope These standards are considered live documents; the ISET and ORS office encourages and welcomes feedback to define these standards better for future procurements. ISET Product: Bus Standards Documents Four documents establish the ORS Phase III bus standards and represent the final deliverables from the Phase III team to the Phase IV team, depicted in Figure 1. A unifying organization, such as the ORS Office at Kirtland AFB will be responsible for the overall ORS system and as such would need to understand the interaction of all of the requirements contained in this set of documents, as well as applicable, complementary efforts by collaborating organizations such as SMC’s Standard Interface Vehicle program. Figure 1: ORS Bus Standards Documents As the mission service provider, this organization will ensure that the combined selection of operations, launch vehicle (LV), payload, and bus form a valid mission implementation for any one specific mission instantiation. Finally, it is expected that any vendor manufacturing a bus under the ORS system would need to be responsive to the applicable information established by all four of the documents. Mission Requirements and CONOPS Document This document represents a top-level definition of the overall ORS mission, as defined by the ISET and consistent with STRATCOM’s initial CONOPS for ORS (May 2007). The primary focus of this document is to outline the orbital environments, envelope the multi-mission support requirements, establish concepts for tactical support and define concepts for operational responsiveness and develop scenarios. Based on these assumptions the system can be decomposed into segments and the document defines the scope of the standards in each segment. It presents the basic CONOPS timelines (Figure 2) for asset call up, integration, launch, and on-orbit operations. It also discusses basic mission definitions, assumptions with which these standards are based and the evolution from the Phase I efforts. Mission “Call-Up” Day 1 Day 2 Day 4 Day 3 Year 1 Integration and Launch Insertion Mission Operations -System Modeling -Mission Planning -P/L Integration to Bus -SV Verification Test -SV Fueling (co-located) Day 5 Day 6 Day 8 Day 7 -SV to LV Integration -Stack Verification Initial Operations in 1 – 4 Orbits -LV Fueling (if Liquid Motor) -Countdown -Launch Insertion -SV Fueling (Disparate Location) -Mission Operations -De-Commission 1 2 3 Figure 2: Top-level Timeline The ORS system is intended to provide responsive launch upon demand to support tactical needs in the theater. In order to achieve the modularity and responsiveness envisioned for an ORS satellite system, the executing agency specifies standardized interfaces between the busses, payloads, and boosters. Initial modularity is also specified for the propulsion system, battery, and tactical communication link. In order to achieve the cost efficiencies envisioned, bus, payload, and booster interfaces would remain constant allowing for multiyear bulk purchases. Spiral changes for new technology insertion would be approx every 2-5 years with modularity expected to increase The envisioned System Architecture is shown Figure 3. Future activities for refining this particular document will be limited to refining the concepts and the concept of operations, and will be heavily dependent on feedback from the ORS community. Jaffe 3 22 Annual AIAA/USU nd Conference on Small Satellites