8 January 2015 - The PanSTARRS Panoramic Survey Telescope and Rapid Response System in Hawaii picks up a 20th magnitude comet in images taken with its 1.8m Ritchey-Chretien telescope. The comet will be at perihelion at 2.0 AU in late March 2015 and has a period of around 90 years. It is reported as MPEC 2015-A42 in the Minor Planet Electronic Circular and CBET 4043 in the Central Bureau for Astronomical Telegrams.

29 January 2015 - Follow-up images taken by PanSTARRS show CBET 4043 is 3 AU closer than predicted. Corrections are issued - perihelion is expected at 1.4 AU in early March with a period of around 160 years. 

5 February 2015 - A second reimaging shows CBET 4043 continues to deviate from its projected course. Perihelion is now expected at 0.5 AU in late February, on a hyperbolic trajectory that does not return to the solar system. 

7-12 February 2015 - Four additional telescopes image CBET 4043.

16 February 2015 - Review of the data confirms the object is not following an unpowered orbit. CBET 4043 is renamed to ESO1. Telescopes and satellites from CNSA, ESA, ISRO, JAXA, NASA, ROSCOSMOS, and other IAU members begin continuous observation of ESO1.

27 February 2015 - ESO1 begins to decelerate.

3 March 2015 - ESO1 separates into 47 observed pieces. Components of ESO1 match velocity and approach Earth orbit.