  We have estimated the largest meteoroids present in major meteor showers from
observations conducted between 2019-2022 by the Geostationary Lightning Mapper
(GLM) instrument on the GOES-R satellites. Our integrated time area products
for the Leonids, Perseids and eta Aquariids are of order 5 x 10^10 km2 hours.
We compute photometric masses for shower fireballs using the approach of
Vojacek et al. 2022 to correct from narrow-band GLM luminosity to bolometric
luminosity and apply the luminous efficiency relation of Ceplecha and McCrosky
1976 at high speeds. Between 2019 and 2022, the showers definitely observed by
GLM were the Leonids, Perseids, and eta Aquariids, with probable detections of
the Orionids and Taurids. We find the largest meteoroids to be of order 7 kg
for the Leonids, 3 kg for the Perseids, and 3 kg for the eta Aquariids,
corresponding to meteoroids of ~ 0.2m diameter. The Orionids and Taurids had
maximum meteoroid masses of 4 kg and 150 kg respectively. The Leonids and eta
Aquariids are well fit by a single power-law with differential mass exponent,
s, of 2.08 +/- 0.08 and 2.00 +/- 0.09 over the mass range 10^-7 < m < 1 kg. All
showers had maximum meteoroid masses compatible with Whipple gas-drag ejection,
with the exception of the Perseids which have much larger meteoroids than
expected which is also consistent with observations from ground based
instruments. This may reflect preferential ejection in narrow jets or possibly
some form of mantle erosion/release in the past for the parent comet,
109P/Swift-Tuttle.
