Hubble Space Telescope
"The Hubble Space Telescope (HST) Case Study" was developed by the United States Air Force Center for Systems Engineering (AF CSE) located at the Air Force Institute of Technology (AFIT) and is accessible at the AFIT HST website. The HST is a 2.4 meter reflecting telescope deployed in low earth orbit that has the ability to observe objects in the optical, ultraviolet, and near-infrared wavelengths. According to the case study, the telescope was planned for retirement in 2010, but additional work on the HST in 2009 (after the case study was written and released) has extended its life until approximately 2014. There is some question as to how the HST will be retired as the final plans have yet to be determined.
Application domains: aerospace, space, communications, exploration, innovative technology, and system of systems.
Application area: product.
Domain Background
“The HST Case Study” includes a brief discussion of the space industry, the progression of telescope development and capability, and other applicable areas.
Case Study Background
The AF CSE, established in 2002 at AFIT, was tasked to develop case studies focusing on the application of systems engineering principles within various aerospace programs (Mattice 2005). The HST study is one of four initial case studies selected by AFIT for development in support of systems engineering graduate school instruction. Each of the case studies employs the Friedman-Sage framework that is comprised of the following nine concept domains:
- requirements definition and management;
- systems architecting and conceptual design;
- system and subsystem detailed design and implementation;
- systems and interface integration;
- validation and verification;
- deployment and post-deployment;
- life cycle support;
- risk assessment and management; and
- system and program management.
The case study also populates a matrix using the Friedman-Sage (Friedman and Sage 2004) nine concept domain framework in the context of the three areas of responsibility listed below:
- systems engineering contractor responsibility;
- shared responsibility; and
- government responsibility.
The Friedman-Sage framework is used in the case study in several areas, including in the discussion of risk and systems engineering management, in relation to Learning Principle 5 (see learning principles below), and in the summary of the case study.
Learning Principles
“The HST Case Study” derived five learning principles (LPs) that address the more broadly applicable areas of systems engineering knowledge. These five LPs inform the areas of the SEBoK that are most strongly related to the case study. The five areas are:
- stakeholder requirements definition (LP1);
- planning (pre-program trade studies) (LP2);
- system integration (LP3);
- life cycle model management (LP4); and
- risk management (LP5).
In addition, the HST study provides a comprehensive perspective on the systems engineering life cycle . It takes the reader through a historical context that begins decades before the HST program was officially started to just beyond the first four HST servicing missions that took place in December 1993, February 1997, December 1999, and March 2002. The study is related to the SEBoK as described in the following sections.
Stakeholder Requirements Definition
Learning Principle 1: Early and full participation by the customer/user throughout the program is essential to success (Mattice vi, 6, 20-21).
This learning principle emphasizes the importance of stakeholder involvement since the lack of adherence to this principle early on in the system development stage of the HST project brought about unwanted consequences in the overall development and successful deployment of the system.
Planning
Learning Principle 2: The use of pre-program trade studies (“phased studies” or “phased project planning” in NASA parlance at the time) to broadly explore technical concepts and alternatives is essential and provides for a healthy variety of inputs from a variety of contractors and government (NASA) centers (vi, 6, 21-23).
This learning principle relates strongly to the impact of non-technical factors on the successful funding of the HST project and, consequently, the implementation of critical trade studies early on in the process. The principle emphasizes that the technical requirements of the program should have been prioritized above the political churn of competing organizations. Also, the areas of the case study that address the Friedman-Sage framework in the concept domain of system and program management fit under this topic.
Systems Integration
Learning Principle 3: A high degree of systems integration to assemble, test, deploy, and operate the system is essential to success and must be identified as a fundamental program resource need as part of the program baseline (vi, 7, 23-33).
The integration challenges of the HST were present throughout the program development. Also the areas of the case study that address the Friedman-Sage framework in the concept domain of systems and interface integration fit under this topic.
Life Cycle Models
Learning Principle 4: Life cycle support planning and execution must be integral from day one, including concept and design phases (vii, 7, 33-37).
The primary example of this principle was the ability to replace a faulty mirror, a completely unanticipated error in the system design, early in the system operational life cycle, in order to bring the telescope to full operation. A second example of this is the service module design – with a primary and a backup – and the redefining of the latest 2009 service mission where the non-functional primary service module was replaced, extending the life of the system even further. The areas of the case study that address the Friedman-Sage framework in the concept domain of life cycle support fit under this topic.
“The HST Case Study” takes the reader through the life cycle of the product development from system concept to deployment. It continues on to follow the sustainability and the current operational state of the system. Sections of the case study cover the historical context, as well as the procurement, development, and subsequent contract award. A time-line is included that begins in 1962 and ends in 1993, the year of the first service mission. The case study does not provide much information on retirement, which is understandable since the system has not yet been retired. Also, the case study was completed in 2005 and does not include an analysis of later events, such as the failure of the primary service module and the 2009 service mission. Another area that is not addressed in the case study is the current operational state of the HST and the impact of the retirement of the shuttle program on the future sustainability of the system.
The case study also includes an analysis that answers the question: “Was the HST, as a total program, a true systems-engineering success and what lessons were learned?” (43). The mixed set of responses are provided by going through specific questions around the concept domains in the Friedman-Sage framework.
Risk Management
Learning Principle 5: For complex programs, the number of players (government and contractor) demands that the program be structured to cope with high risk factors in many management and technical areas simultaneously (vii, 7, 37-42).
The HST study supports this principle by pointing out that Lockheed Martin was held responsible for the risk of the optical systems even though Perkin-Elmer was the technical expert in this area. This inevitably led to the HST going into orbit with the primary mirror defect still undetected. The areas of the case study that address the Friedman-Sage framework in the concept domain of risk assessment and management fit under this topic.
Summary
“The HST Case Study” provides a comprehensive perspective on the systems engineering life cycle, and can be used for detailed instruction in the areas of stakeholder requirements definition, technical planning (Pre-Program Trade Studies), system integration, life cycle model management, and risk management. Further, the case study provides a useful example of the rising cost of defect correction through successive life cycle phases, demonstrating how an error (in test fixture specification) that could have been fixed for $1,000 at the design stage, or detected and fixed with a $10 million investment in an end-to-end test of the telescope on the ground, ended up costing $1 billion to fix when the system was in service.
References
Works Cited
Friedman, G. and A. Sage. 2004. “Case Studies of Systems Engineering and Management in Systems Acquisition.” Systems Engineering. 7(1): 84-96.
Mattice, J. “Hubble Space Telescope Case Study,” last modified March 10, 2005. Accessed on September 11, 2011. Available at http://www.afit.edu/cse/cases.cfm?case=18&a=detail.
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