The water production rate of Rosetta target Comet 67P/Churyumov-Gerasimenko near perihelion in 1996, 2002 and 2009 from Lyman α observations with SWAN/SOHO

While the perihelion distance to sun decreased continuously (1.300, 1.292, 1.246 AU respectively for 1996, 2002, 2009), the average production Q(H2O) just after perihelion did not increase accordingly: 1.30×1028, 1.70×1028, and 5.65×1027 mol s−1. Comparison with 1982 IUE measurement of 6×1027 mol s−1 suggests no rapid aging of the comet, and we may expect a similar level of activity at the next perihelion in August 2015. The production rate in 2009 showed a peak around 16.4 days post-perihelion, with a suggestion of a second peak at ~40 days, and a somewhat reduced rate in between (though SWAN measurements are incomplete). These measurements may help in planning of Rosetta activities around the next perihelion.