hours every 2 to 4 weeks. Scientists received a few minutes of good engineering data on November 24, 1995, but then lost final contact once Earth moved out of view of the spacecraft's antenna. Current status As of January 20, 2023, Pioneer 11 is estimated to be from the Earth and from the Sun; and traveling at (relative to the Sun) and traveling outward at about 2.36 AU per year. The spacecraft is heading in the direction of the constellation Scutum near the current position (January 2023) RA 18h 54m dec -8° 59' (J2000.0), close to Messier 26. In 928,000 years, it will pass within 0.25pc of the K dwarf TYC 992-192-1, and will pass near the star Lambda Aquilae in about four million years. Pioneer 11 has now been overtaken by the two Voyager probes launched in 1977, and Voyager 1 is now the most distant object built by humans. Pioneer anomaly Analysis of the radio tracking data from the Pioneer 10 and 11 spacecraft at distances between 20 and 70 AU from the Sun has consistently indicated the presence of a small but anomalous Doppler frequency drift. The drift can be interpreted as due to a constant acceleration of directed towards the Sun. Although it is suspected that there is a systematic origin to the effect, none was found. As a result, there is sustained interest in the nature of this so-called "Pioneer anomaly". Extended analysis of mission data by Slava Turyshev and colleagues has determined the source of the anomaly to be asymmetric thermal radiation and the resulting thermal recoil force acting on the face of the Pioneers away from the Sun, and in July 2012 the group of researchers published their results in the Physical Review Letters scientific journal. Pioneer plaque Pioneer 10 and 11 both carry a gold-anodized aluminum plaque in the event that either spacecraft is ever found by intelligent lifeforms from other planetary systems. The plaques feature the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft. Commemoration In 1991, Pioneer 11 was honored on one of 10 United States Postage Service stamps commemorating unmanned spacecraft exploring each of the then nine planets and the Moon. Pioneer 11 was the spacecraft featured with Jupiter. Pluto was listed as "Not yet explored". Gallery See also Cassini–Huygens List of artificial