  C/2020 F3 (NEOWISE) was discovered in images from the Near Earth Object
program of the Wide-Field Infrared Survey Explorer (NEOWISE) taken on 27 March
2020 and has become the Great Comet of 2020. The Solar Wind ANisotropies (SWAN)
camera on the Solar and Heliospheric Observatory (SOHO) spacecraft, located in
a halo orbit around the Earth-Sun L1 Lagrange point, makes daily full-sky
images of hydrogen Lyman-alpha. Water production rates were determined from the
SWAN hydrogen Lyman-alpha brightness and spatial distribution of the comet
measured over a 4-month period of time on either side of the comet's perihelion
on 3 July 2020. The water production rate in s^-1 was moderately asymmetric
around perihelion and varied with the heliocentric distance, r, in au as
(6.9+/-0.5) x 10^28 r^-2.5+/-0.2 and (10.1+/-0.5) x 10^28 r^-3.5+/-0.1 before
and after perihelion, respectively. This is consistent with the comet having
been through the planetary region of the solar system on one or more previous
apparitions. A water production rates as large as 5.27 x 10^30 s^-1 were
determined shortly after perihelion, once the comet was outside the solar
avoidance area of SWAN, when the comet was 0.324 au from the Sun.
