GCN Circular 931

As many of you are no doubt aware, the Near Earth Asteroid Rendezvous
mission executed a controlled descent to the surface of the asteroid
Eros on February 12, bringing the mission to a successful end.
However, this has also deprived the 3rd Interplanetary Network of the
second distant point which is required to produce small error boxes.
The network now consists of Ulysses, in heliocentric orbit, BeppoSAX
(GRBM), HETE-II, and RXTE, in low earth orbit, and Konus-Wind, at the
L1 Lagrange point.  In this configuration, the IPN can produce (as it
did prior to NEAR),

a) single annuli (using Ulysses and one other spacecraft), which will
help reduce the sizes of the error boxes derived from HETE-II, RXTE, and
the BeppoSAX WFC and NFI, and

b) long, narrow error boxes (using Ulysses, Konus, and a near-Earth
spacecraft).

In general, our policy will be NOT to issue GCN notices for the bursts
detected by the IPN in this mode unless 

1) they are imaged by BeppoSAX, HETE-II, or RXTE, 

2) they are very unusual in some sense, 

3) they are suspected to originate from known or new soft gamma
repeaters, or

4) potential users of such notices notify us of their
requirements.

(We do, however, intend to triangulate these events
and produce a catalog of them eventually.  We will also begin
work immediately on a catalog of NEAR bursts.)

The Mars Odyssey '01 mission, to be launched in April, has two
independent gamma-ray burst detection systems.  Because the mission
goes farther from Earth than NEAR, and because the detection systems
have better time resolution, this rejuvenated network promises to
perform better than the old one.  Due to financial constraints, there
is still some uncertainty about the duty cycles of these systems during
the 9 month cruise phase to Mars.  (Although once they are in orbit,
they are expected to operate continuously for one Mars year, i.e.
through 2003.)  We look forward to continuing to issue small error box
notices, perhaps as soon as a few months from now.


Kevin Hurley (on behalf of the Ulysses GRB team)
Thomas Cline (on behalf of the NEAR GRB team)
Scott Barthelmy (on behalf of the GCN)