GCN Circular 2923

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks
on behalf of Konus-Wind and Helicon/Coronas-F teams, and
T. Cline on behalf of the Konus-Wind team report:

We present an evidence of Helicon-Coronas-F detection of the giant
outburst from SGR1806-20 which was scattered back from the Moon.
At the time of the outburst SGR1806-20 was occulted by the Earth
for Coronas-F. A short burst triggered Helicon at 21:30:29.303s UT on
Dec 27. A time delay between Konus-Wind and Helicon-Coronas-F detections
is -7.70 s. This value corresponds exactly to burst travelling time from
  the Wind to the Moon and back to the Coronas-F. The spectrum of the
event detected by the Helicon is highly unusual. It looks like a broad
assymetric line peaked at ~100 keV. Apparently such a shape corresponds
to back-scattering peak of a huge initial pulse of the outburst. The
fluence of event is about 7.5x10^-7 erg cm-2 in 25-400 keV range.