Hill Observatory , Australia, and by Rui Gonçalves at Linhaceira Observatory in Portugal. Lightcurve analysis gave a well-defined rotation period of hours with a brightness variation of magnitude, significantly higher than previous observations had measured (). The observers also found no indication of a previously speculated companion. The result supersedes observations from July 2001, when both Robert Stephens and Laurent Bernasconi determined a period of and hours with an amplitude of and magnitude, respectively. Diameter and albedo According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Erda measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.1942 and a diameter of 36.26 kilometers based on an absolute magnitude of 9.6. An alternative mean-diameter measurement published by the WISE team gives () with an albedo of (). On 17 April 2010, an asteroid occultation gave a best-fit ellipse dimension of 36.00 × 36.0 kilometers, while a second observation on 15 September 2014, measured an ellipse of 38.00 × 38.0 kilometers These timed observations are taken when the asteroid passes in front of a distant star. References External links Lightcurve Database Query (LCDB), at www.minorplanet.info Dictionary of Minor Planet Names, Google books Asteroids and comets rotation curves, CdR – Geneva Observatory, Raoul Behrend Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center 000894 Discoveries by Max Wolf Named minor planets 19180604