In 2017, 2018, and 2019, comets 46P/Wirtanen, 45P/Honda–Mrkos–Pajdusakova, and 41P/Tuttle–Giacobini–Kresak all had perihelion passages. Their hydrogen comae were observed by the Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyα camera on the SOlar and Heliospheric Observer (SOHO) satellite: comet 46P for the fourth time and comets 45P and 41P for the third time each since 1997. Comet 46P/Wirtanen is one of a small class of so-called hyperactive comets whose gas production rates belie their small size. This comet was the original target comet of the Rosetta mission. The SWAN all-sky hydrogen Lyα camera on the SOHO satellite observed the hydrogen coma of comet 46P/Wirtanen during the apparitions of 1997, 2002, 2008, and 2018. Over the 22 yr, the activity decreased and its variation with heliocentric distance has changed markedly in a way very similar to that of another hyperactive comet, 103P/Hartley 2. Comet 45P/Honda–Mrkos–Pajdusakova was observed by SWAN during its perihelion apparitions of 2001, 2011, and 2017. Over this time period, the activity level has remained remarkably similar, with no long-term fading or abrupt decreases. Comet 41P/Tuttle–Giacobini–Kresak was observed by SWAN in its perihelion apparitions of 2001, 2006, and 2017 and has decreased in activity markedly over the same time period. In 1973 it was known for large outbursts, which continued during the 2001 (two outbursts) and 2006 (one outburst) apparitions. However, over the 2001 to 2017 time period covered by the SOHO/SWAN observations the water production rates have greatly decreased by factors of 10–30 over corresponding times during its orbit.

在2017年，2018年和2019年，46P / Wirtanen，45P / Honda-Mrkos-Pajdusakova和41P / Tuttle-Giacobini-Kresak彗星均具有近日点通过。其氢comae是由太阳风各向异性（SWAN）全天空氢Ly的观察α第四次和彗星45P和41P的第三次各自1997年以来彗星46P：在太阳和日光层观察员（SOHO）卫星相机。 46P / Wirtanen彗星是一类所谓的高活性彗星中的一种，其气体产生率掩盖了它们的小尺寸。这颗彗星是罗塞塔任务的最初目标彗星。的SWAN全天空氢Ly的αSOHO卫星上的相机在1997年，2002年，2008年和2018年的幻影中观测到46P / Wirtanen彗星的氢昏迷。在过去的22年中，该活动减少了，其随日心距的变化显着地类似于SWAN在2001年，2011年和2017年的近日点幻影中观测到另一颗活动过度的彗星103P / Hartley 2的彗星和45P / Honda–Mrkos–Pajdusakova彗星。在此期间，活动水平一直非常相似，没有长期褪色或突然减少。SWAN在2001年，2006年和2017年的近日点观测中观测到41P / Tuttle–Giacobini–Kresak彗星，并且在同一时期内活动明显减少。1973年以大爆发而闻名，这种爆发在2001年（两次爆发）和2006年（一次爆发）幻影期间一直持续。然而，