GCN Circular 6461
H. Swan (U Mich), I. Smith (Rice), C. Akerlof (U Mich), and M. Skinner (Boeing) report on behalf of the MARGE collaboration: The AEOS Burst Camera (ABC) on the AEOS telescope, located at the Maui Space Surveillance System on Haleakala, observed the fading counterpart to GRB070518 (Swift trigger 279592(GCN 6415)). The images are unfiltered 10s exposures which started at 14:55:49 UT (~29 minutes after the trigger) and ended at 15:04:00 UT. After coadding our images in sets of 5, we detect the OT first identified by C. Guidorzi et al (GCN 6415). A preliminary analysis gives a magnitude of approximately 20.0 +/-0.1 at a mid time of 14:56:32 UT. We calibrated the OT to the USNO-A2.0 R band magnitude of the nearby 18.7 mag star located at (J2000) RA = 16:56:47.4373, DEC = +55:17:45.610. Our observations are consistent with the other optical observations. Using our data, and the optical data from P. A. Price and T. Minezaki (GCN 6443), L. P. Xin et al. (GCN 6416), M. Jelinek et al. (GCN 6418), F. Terra et al. (GCN 6458), and S. Covino et al. (GCN 6426), we find that the OT has a power-law decay index of 0.74.