Pioneer H

Reconstructed full-scale mock-up Pioneer 10 / 11 spacecraft at the National Air and Space Museum

Pioneer Hwas a proposedspace probefor theUSPioneer program.If it had been approved, it would have been launched in 1974 and have been designated Pioneer 12; that designation was later applied to thePioneer Venus Orbiter.

History

The Pioneer flight spare at NASM, behindJames A. Van Allen

As planning for the Pioneer 10 and 11 missions progressed, mission scientists found themselves desiring a third probe. In 1971, a formal mission study was proposed for a spacecraft to be launched toJupiterin 1974, where it would use the gas giant as agravitational slingshotto travel outside theecliptic.This was the first Out-Of-The-Ecliptic mission (OOE) proposed, for Jupiter and solar (Sun) observations.

NASA/Ames Research Center would have managed the project. TheNASAcontractorTRW Systems Group(formerly Space Technology Laboratories) would have constructed the Pioneer H probe from the flight-qualified spare components intended for the Pioneer F and G probes (designatedPioneer 10andPioneer 11after launch), along with a small amount of new build hardware.

TRW assembled the spare components into a new spacecraft, but NASA management did not approve the mission proposal, and it was never launched. In 1976 NASA transferred the probe (withoutRTG) to theSmithsonian Institution.In January 1977, it was moved to theNational Air and Space Museum,where it was eventually displayed as a replica of Pioneer 10.

Successor missions

ThePioneer Hmission concept was finally realized with theUlyssesmission, which achieved the OOE orbit originally envisioned for Pioneer H. TheJunomission, currently at Jupiter in a polar orbit, is taking themagnetometerobservations of Jupiter's poles that Pioneer H would have performed.

Current location

ThePioneerflight spare hangs in the Milestones of Flight Gallery at theNational Air and Space MuseuminWashington, D.C.,serving as a stand-in for the Pioneer 10 probe.

While described in official Smithsonian records as a "replica", the spacecraft was considered fully functional by Pioneer mission planners (though itsRTGswere never installed). Mark Wolverton quotesJames Van AlleninThe Depths of Space:

We mounted an intensive campaign to launch the flight-worthy spare spacecraft and its instrument complement on a low-cost, out-of-ecliptic mission via a high-inclination flyby of Jupiter. However, our case fell on deaf ears at NASA headquarters, and the spare spacecraft now hangs in the main gallery of the National Air and Space Museum, at 1AUand zero ecliptic latitude.

External links

• The Depths of Space: The Story of the Pioneer Planetary Probes, Mark Wolverton, 2004Archived2007-05-15 at theWayback Machine
• National Air and Space Museum - Pioneer 10 - Milestones of FlightArchived2009-05-23 at theWayback Machine
• Assembling for NASM the Pioneer 10 replica
• International Solar Polar mission, 1979