Normalizations

What NASA includes in its planetary science budget has changed over the years, which makes it difficult to perform apples-to-apples comparisons. This dataset attempts to normalize out these differences somewhat, in order to provide a clearer picture of how planetary science spending priorities change over time.

It's impossible to normalize budgetary data without imposing a personal opinion on "what matters", or what is worth normalizing. As a consequence, any normalizations that add or subtract to the original budget request are noted within the spreadsheet.

However, there are three normalizations that deserve mention:

Expendable launch vehicle costs are always included in the mission total and in the annual planetary program costs. Launch costs associated with the STS (Space Shuttle) are not included, though they are retained as a reference within each fiscal year entry in the dataset.

Deep Space Network infrastructure and operations costs are removed from the program totals for the fiscal years 2003 - 2007.

Development costs for the Pioneer program are retained in the planetary program costs for fiscal years 1968 and 1969.

Estimated and Missing Data

Accounting and reporting variations over NASA's history occasionally leads to gaps in cost data, particularly for annual operating costs of planetary missions. In certain situations, estimated values were used to fill in these missing sections. Estimated data is always referenced with italics in the spreadsheet, with context for the estimate noted in the source tabs.

Additionally, during the late 1990s through the early 2000s, NASA integrated management of its entire science portfolio (astrophysics, space physics, planetary science, and Earth science), resulting in a significant loss of fidelity of planetary-related research, operations, and management costs. That makes reconstructing a consistent planetary science budget during this period difficult using publicly-available data. Work by Jason Callahan fills in the "actual" amounts spent on the planetary science program during this period.

The extended operations costs for many missions are difficult to reconstruct. For operations costs that are not explicitly reported, many are estimated based on official press releases detailing total spending over a multi-year period. Public reporting markedly improved starting in FY 2013 due to a revised format of NASA budget estimates.

If you have corrections or can provide reliable sources for missing or incomplete data—particularly for extended mission operations—please contact [email protected].

Other considerations

Since this dataset is based on publicly-reported obligations, which are contracted amounts that can be spent over a multi-year timeframe, the reported data may differ slightly from outlays, which is when the money actually moved out the door. Unexpected mission-ending events may also impact reported obligations, allowing funds to shift to other projects or go unspent. Generally, however, the obligations track relatively closely to official mission costs as reported by NASA.

A significant shift in cost reporting occurred in fiscal year 2004, when NASA shifted into a full cost-accounting method for its projects. Previously, overhead costs such as facility use and NASA employee time were accounted for in a separate, consolidated NASA account. In FY 2004 NASA began assigning these costs to individual projects in proportion to the resources consumed by that project. The consequence of this accounting change is that missions developed after FY 2004 will look more expensive, on average, than similar projects implemented prior, since they now carry overhead costs of NASA operations within them. There is no easy way to normalize these two eras of NASA accounting. However, a rule-of-thumb approach is to add 10% to the overall cost of projects implemented prior to the full-cost accounting era. It's not exact, but it gets you in the ballpark.

Sources

Cost data from fiscal years 1959 - 1997 and from 2002 onwards are from public NASA budget estimates submitted to Congress, which list obligations (contracted spending amounts) for the fiscal year 2 years previous. For example, the FY 1969 budget justification lists obligated program amounts in FY 1967. NASA Headquarters' Historical Reference Collection digitized these budget documents, which The Planetary Society has made available for download.

Planetary science program total "actuals" from fiscal years 1997 to 2001 are from data presented by Jason Callahan, "Budgeting for Exploration: History and Political Economy in Space Science 1959-2010", at the AAS 45th Meeting of the Division for Planetary Sciences, Denver, Colorado. October 7, 2013.

Notable mission events and dates were drawn from Asif Siddiqi's Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016, published by the NASA History Program Office in 2018.