U.S. lawmakers eager to increase the number of Defense Department launches available for competition are drawing a bead on an aging weather satellite as a likely candidate payload.

The House version of the Defense Authorization Act for Fiscal Year 2015 would direct the U.S. Air Force to initiate a competitive procurement of a launch for the Defense Meteorological Satellite Program (DMSP)-20 satellite, the last in a series whose legacy dates back to the 1960s. The Air Force in April launched the penultimate DMSP satellite but has been noncommittal about DMSP-20.

In the House bill, support for the competitively awarded launch would come at the expense of a replacement weather satellite system the Air Force hopes to begin developing next year.

Competition in the U.S. government launch business is a hot topic these days given longstanding frustrations over the high costs associated with the incumbent provider, United Launch Alliance, and the rise of Space Exploration Technologies Corp. to challenge that monopoly. Current Air Force plans call for putting the launches of at least seven operational satellites up for bid in the next couple of years, but competition advocates are looking for more.

DMSP-20 would seem like an ideal candidate: Its weight and orbit are well within the capability of SpaceX’s relatively low-cost Falcon 9, which could be certified to launch U.S. national security payloads by the end of the year. The relatively low priority the Air Force has assigned to the satellite means the service should feel comfortable launching it on something other than the Atlas 5 or Delta 4, ULA’s workhorse rockets.

Meanwhile, uncertainty surrounds the Atlas 5, which uses a Russian-built main engine whose availability has come into question amid deteriorating relations between Washington and Moscow. The Atlas 5 is cheaper than comparably sized versions of the Delta 4 and also is able to launch missions that otherwise would require the Delta 4 Heavy variant, a hugely expensive vehicle with three core stages. As such, the Air Force is looking at how it might shuffle its manifest to preserve the Atlas 5 for those types of missions while expanding production of the Delta 4.

This, too, argues in favor of putting the DMSP-20 launch up for grabs. 

But there are equally compelling counterarguments. 

According to Gen. William Shelton, commander of Air Force Space Command, for example, the satellite is specifically configured to launch on the Delta 4 or Atlas 5. Reconfiguring the craft to launch atop another vehicle — presumably the Falcon 9 — will take a year and cost tens of millions of dollars, he said.

More importantly, it is not clear at this point whether it is worth launching the satellite at all. DMSP-20, like the recently launched DMSP-19, was built in the 1990s for a mission whose requirements are in many cases being met by other sensors, including civilian spacecraft. This is a large part of the reason that the Air Force is leaning toward a DMSP follow-on system that focuses on the measurements that are not available from other sources. This satellite presumably would incorporate the latest technology and might be small enough to launch atop a low-cost rocket like a Minotaur, which utilizes excess missile assets.

True, the Air Force spent hundreds of millions of dollars building, storing and refurbishing the final two DMSP satellites. But sunk investments are in and of themselves poor justifications for future expenditures. DMSP-20 certainly would not be the first Air Force space vehicle to wind up as a museum piece, if it comes to that.

One alternative that doesn’t seem to make much sense is to stick with the notional Air Force plan to launch DMSP-20 in 2020. That would cost the service hundreds of millions of dollars in storage fees, all for a satellite that by 2020 will contain components that in some cases are more than 20 years old. 

But launching the satellite at an earlier date — if it’s just for the sake of launching — doesn’t make much sense either.

The Air Force and civilian U.S. National Oceanic and Atmospheric Administration are in the midst of a study on the future of DMSP-20 that will consider the pros and cons of going through with the launch. Congress should wait until the results of that study are in before prescribing a path for the satellite.