The major issue is that you have nearly no idea when/where these events will occur, and they are really rare to begin with. Add the distances that these things occur at and your error bars go through the roof[2]. Still, over a VERY long time and with a LOT of these detectors spread about the Sol system (and likely a bit further out), you can get the results you'd need.
It's not cheap or easy or timely. But with 12 orders of magnitude to go, it's a lot cheaper, easier, and more timely than trying to build an accelerator with Jupiter in the way :)
[0] as in, not next to the Sun, Earth, Moon, near gravitational perturbers, etc.
[1] https://en.wikipedia.org/wiki/Astrophysical_jet
[2] http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/lenseq.htm...