Since it was launched in 1990, the Hubble Space Telescope has sent back images of space that have made a significant contribution to our understanding of the universe. The telescope uses pointing precision, powerful optics, and state-of-the-art instruments to explore the visible, ultraviolet, and near-infrared regions of the electromagnetic spectrum. To keep it at the forefront of astronomical research and extend its operational life, Hubble’s instruments have been upgraded through a series of shuttle servicing missions. The fifth and final planned servicing mission was intended to install new science instruments, replace the telescope’s insulation, and replace the batteries and gyroscopes. According to NASA, the lifetime of the observatory on orbit is ultimately limited by battery life, which may extend into the 2007-2008 time frame, but scientific operations are limited by the gyroscopes that stabilize the telescope—whose lifetimes are more difficult to predict. NASA forecasts that the Hubble will likely have fewer than three operating gyroscopes by mid-2006, and fewer than two by mid-2007. In response to congressional concerns about NASA’s decision to cancel the servicing mission, NASA requested that the National Research Council conduct an independent assessment of options for extending the life of the Hubble Space Telescope. In May 2004, the Council established a committee to assess the viability of a shuttle servicing mission, evaluate robotic and ground operations to extend the life of the telescope as a valuable scientific tool, assess telescope component failures and their impact, and provide an overall risk-benefit assessment of servicing options. In an interim report issued in July 2004, the committee urged NASA to commit to a Hubble servicing mission that accomplishes the objectives of the canceled servicing mission and to take no actions that would preclude using a space shuttle to carry out this mission. According to a NASA official, the agency is not actively pursuing the shuttle servicing option but is not precluding it. NASA is currently evaluating the feasibility of performing robotic servicing of the Hubble Telescope. To facilitate the evaluation, the agency has formulated a robotic mission concept, which includes a vehicle comprised of a robotic servicing module and another module that can be used to eventually de-orbit the telescope. The potential task list of activities for robotic servicing includes replacing the gyroscopes and batteries, installing new science instruments, and de-orbiting the observatory at the end of its life. According to a NASA official, contracts to facilitate the robotic mission were recently awarded for work to begin on October 1, 2004. The CAIB concluded that the Columbia accident was caused by both physical and organizational failures. The Board’s 15 return to flight recommendations necessary to implement before the shuttle fleet can return to flight primarily address the physical causes of the accident and include eliminating external tank debris shedding and developing a capability to inspect and make emergency repairs to the orbiter’s thermal protection system. NASA publishes periodic updates to its plan for returning the shuttle to flight to demonstrate the agency’s progress in implementing the CAIB recommendations. The most recent update is dated August 27, 2004. This update identifies the first shuttle flight as occurring in spring 2005. NASA does not currently have a definitive cost estimate for servicing the Hubble Telescope using the shuttle. The agency focused on safety concerns related to a servicing mission by the space shuttle in deciding not to proceed, and did not develop a cost estimate. At our request NASA prepared an estimate of the funding needed for a Hubble servicing mission by the space shuttle. NASA could not provide documented support for its estimate. The agency recognizes that there are many uncertainties that could change the estimate. NASA has now begun to explore the costs and benefits of various servicing alternatives, including robotic servicing, which should enable NASA to make a more informed decision regarding Hubble’s future. At our request NASA began development of an estimate of the funding needed for a shuttle servicing mission to the Hubble. The estimate provided captures additional funds over and above NASA’s fiscal year 2005 budget request that would be required to reinsert the mission in the shuttle flight manifest for launch in March 2007. The estimate does not include funding already expended to support the canceled servicing mission and develop the science instruments. NASA has determined that the additional funds needed to perform a shuttle servicing mission for Hubble would be in the range of $1.7 billion to $2.4 billion. According to NASA, this estimate is based on what it might cost, but it does not take into account the technical, safety, and schedule risks that could increase the cost and/or undermine the viability of the mission. For example, NASA cites uncertainties related to two safety-related requirements: inspection and repair and crew rescue mission capabilities that would be autonomous of the International Space Station and for which NASA currently has not formulated a design solution. In addition, NASA cautions that it did not examine whether design solutions could be accomplished in time to service Hubble before it ceases operations. Table 1 shows NASA’s budget estimate phased by fiscal year (FY) for shuttle servicing of the Hubble Space Telescope, including ranges for some of the estimates. While we did not independently verify each component of NASA’s estimate, we requested that NASA provide the analytical basis and documentary support for selected portions of the estimate, primarily those with large dollar values. NASA could not provide the requested information. For example, NASA officials told us that the Hubble project’s sustaining engineering costs run $9 to10 million per month, but they were unable to produce a calculation or documents to support the estimate because they do not track these costs by servicing mission. We also requested the basis of estimate for the costs to delay shuttle phase-out and for tools development for vehicle inspection and repair without the International Space Station (a component of extravehicular activity above). In response, NASA provided the assumptions upon which the estimates were based and stated that the estimates were based on information provided by Johnson Space Center and Kennedy Space Center subject matter experts. NASA also added that rigorous cost estimating techniques could not be applied to the tools development estimate because a rescue mission currently is only a concept. No analytical or documentary support was provided. In estimating the cost for the autonomous inspection and repair and rescue mission capabilities, NASA used a 30 to 50 percent uncertainty factor because of the very high uncertainty in the cost of developing and conducting a mission that is not adequately defined—i.e., NASA’s estimate of $425 million plus 50 percent equals the $638 million upper range shown in the table above for these two items added together. As with the other estimates for which we requested analytical and documentary support, NASA was not able to provide it because the agency could not do a risk analysis without a design solution, according to a NASA official. The lack of documented support for portions of NASA’s estimate increases the risk of variation to the estimate. Further, NASA recognizes that there are many uncertainties that could change the current estimate. The 2004 NASA Cost Estimating Handbook states that cost analysts should document the results of cost estimates during the entire cost estimating process and that the documentation should provide sufficient information on how the estimate was developed so that independent cost analysts could reproduce the estimate. According to the handbook, the value of the documentation and analysis is in providing an understanding of the cost elements so that decision-makers can make informed decisions. Recently, we also reported that dependable cost estimates are essential for establishing priorities and making informed investment decisions in the face of limited budgets. Without this knowledge, a program’s estimated cost could be understated and thereby subject to underfunding and cost overruns, putting programs at risk of being reduced in scope or requiring additional funding to meet their objectives. Since we began our review, attention has focused on alternatives to a shuttle mission, such as robotic servicing of Hubble. NASA has formed a team to evaluate Hubble servicing alternatives, including cost information. This analysis should enable NASA to make a more informed decision about Hubble’s future and facilitate NASA’s evaluation of the feasibility of robotic servicing options. Currently, NASA has developed budget estimates for implementing the CAIB recommendations required to return the space shuttle to flight but not for all of the CAIB recommendations. NASA provided us with documentary support for portions of the return to flight estimate, but we found it to be insufficient. According to NASA, the agency’s cost for returning the shuttle to flight, which is slightly over $2 billion, will remain uncertain until the completion of the first shuttle missions to the International Space Station in fiscal year 2005. NASA’s return to flight activities involve enhancing the shuttle’s external tank, thermal protection system, solid rocket boosters, and imagery system to address the physical cause of the Columbia accident—a piece of insulating foam that separated from the external tank and struck a reinforced carbon-carbon panel on the leading edge of the orbiter’s left wing. To address this cause, NASA is working to eliminate all external tank debris shedding. Efforts are also in place to improve the orbiter’s thermal protection system, which includes heat resistant tiles, blankets, and reinforced carbon-carbon panels on the leading edge of the wing and nose cap of the shuttle, to increase the orbiter’s ability to sustain minor debris damage. NASA is also redesigning the method for catching bolts that break apart when the external tank and solid rocket boosters separate as well as providing the capability to obtain and downlink images after the separation. NASA and the United States Air Force are working to improve the use of ground cameras for viewing launch activities. Table 2 shows NASA’s budget estimates for return-to-flight activities. However, the majority of NASA’s budget estimates for returning the shuttle to flight are not fully developed—including those for fiscal year 2005—as indicated by the agency’s internal approval process. The Program Requirements Control Board (PRCB) is responsible for directing studies of identified problems, formulating alternative solutions, selecting the best solution, and developing overall estimates.