Pioneer 6

Purpose

Pioneer 6 was part of a fleet designed to gather the first in-depth readings of the solar wind, the sun's magnetic field, and cosmic rays. It examined positive ions and electrons in the solar wind, interplanetary electron density, solar and galactic cosmic rays, and the interplanetary magnetic field. The spacecraft served in the first space-based network for monitoring solar weather, delivering practical data on solar storms that disrupt communications and power on Earth. Its findings helped scientists better understand stellar processes and the solar wind's structure and flow.

Communications

By ground command, one of five bit rates (512, 256, 64, 16, and 8 bit/s), one of four data formats, and one of four operating modes could be selected. Three of the four data formats contained primarily scientific data consisting of 32 seven-bit words per frame; one format was for the two highest bit rates, another for the three lowest, and a third contained only radio propagation experiment data. The fourth format held mainly engineering data. The four operating modes were real-time, telemetry store, duty cycle store, and memory readout.

In real-time mode, data were sampled and transmitted directly. In telemetry store mode, data were stored and transmitted simultaneously. In duty-cycle store mode, a single frame was collected and stored at 512 bit/s, with intervals between frames variable by ground command from 2 to 17 minutes, providing partial coverage for up to 19 hours. In memory readout mode, data were read out at a bit rate appropriate to the satellite's distance from Earth.

Timeline and current status

Pioneer 6 was launched on December 16, 1965, into a circular solar orbit with a mean distance of 0.8 AU. Its original design life expectancy was only 6 months. The prime traveling-wave tube (TWT) failed sometime after December 1995, and in July 1996 the spacecraft was commanded to the backup TWT. On October 6, 1997, it was tracked with the 70 meter Deep Space Station 43 in Australia; the MIT and ARC Plasma Analyzers and the cosmic ray detector from the University of Chicago were turned on and working.

A successful telemetry contact was made on December 8, 2000, lasting about two hours, to celebrate 35 years of continuous operation. As of March 26, 2007, NASA described Pioneer 6 as 'extant', but there has been no contact since December 8, 2000. At that time it had operated for 12,758 days, making it the oldest operating space probe until it was surpassed by Voyager 2 on August 13, 2012. The program has been touted as one of the least expensive of all NASA spacecraft programs in terms of scientific results per dollar spent.

Did You Know?

• Pioneer 6 was identical in design to Pioneers 7, 8, and 9, each being a spin-stabilized 0.94 m diameter × 0.81 m tall cylinder with a 1.8 m long magnetometer boom.
• The spacecraft's spin axis was perpendicular to the ecliptic plane and pointed toward the south ecliptic pole, with a spin rate of about 60 RPM.
• A fifth spacecraft, Pioneer E, was lost in a launch accident on August 27, 1969, when the launch vehicle was destroyed by range safety after hydraulics in the first stage failed.