One of the fundamental questions for any proposed space mission is "How much will it cost?" - usually closely followed by "Is it worth it?" Various models exist to estimate the cost of space missions [Larson92] but those based on 'traditional' spacecraft tend to considerably overestimate the cost of small spacecraft built to the 'faster, better, cheaper' paradigm. Reducing Space Mission Cost thus quotes a special small-satellite cost model developed by The Aerospace Corporation to estimate costs for this sort of mission [Wertz96].

The version 8 Small Satellite Cost Model is based on details of 29 small satellites launched or developed since 1991. It uses 11 spacecraft parameters grouped into 6 equations that each provide a cost estimate for the entire spacecraft. Each estimate has an associated standard error based on how well it predicts costs for the database of actual satellites. This is used together with the individual estimates to provide a weighted estimate of spacecraft cost. Table 19.1 lists the model parameters (grouped by the estimate they contribute to) together with the relevant values for this project and the resulting cost estimates, plus the model's quoted standard errors.

The weighted cost can be found from the individual costs c and errors via the weighted estimate

(19-1)

whilst the weighed cost error is found by

(19-2)

For this mission, the weighted cost estimate is $13.625 million with a weighted error of $12.134 million. The large error reflects the considerable variation in the different individual cost estimates within the model. However, assuming that no error is likely to be an underestimate the overall spacecraft cost is likely to be in the range $2.5 million to $26 million, with (as quoted in Section 4) a launch cost of $5 million to $15 million. The overall project cost is thus estimated as being in the range $7.5 million to $41 million, with (if low-cost launch systems become available in the next few years) a reasonable target cost of $18.5 million.