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The first major freeze point in the production process is at L-15 months, at which time the flight is baselined in the FDRD. The baselined items include the launch date, Orbiter to be used, and major payloads to be flown. Design and engineering conducted after the FDRD freeze point is based on this information.

At L-7.7 months, a CIR is held and is the second major freeze point in the production process. During the CIR, among the major design and engineering products that are frozen are the integration hardware design, the Orbiter vehicle configuration, flight design, and software requirements. Further design and engineering conducted after the CIR freeze point is based on these products.

The third major freeze point in the production process is the Flight Planning and Stowage Review and occurs at L-5 months. At this time, the crew activity timeline and the crew compartment configuration, which includes middeck payloads and payload specialist assignments, are frozen. Further design and engineering conducted after the L-5 review freeze point is based on these products.

b. Factors Causing Manifest Changes

Changes to the manifest are a reaction to some stimuli. The stimulus may come from any or all of the following categories:

• Hardware problems
• Customer requestes
• Operational constraints
• External factors

When changes occur, the program must choose a response to the problem and accept the consequences of that response. The program has two choices: (1) optimize and facilitate the payload or response to customer needs; or (2) minimize the impact to STS operations and put the problem response outside the production template. If the first option is selected, the consequences will include short-term and/or long-term impacts to the STS. The following paragraphs dicuss these consequences.

Hardware problems can cause significant impacts to manifesting. When they occur, usually little can be done except to implement a fix to the problem and to accommodate the system to the consequences. These consequences will often have a long-term rippling effect, as will be shown later.

Customer requests also can cause significant impact on manifesting. These requests, often for a later than scheduled launch date, are made as late as NASA will allow.

Operational constraints impose requirements on STS missions that require remanifesting. Cargo weight growth or Orbiter landing weight can cause an Orbiter assignment to be changed. With each reassignment, accompanying launch date changes to other cargos can

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