In a series of four tweets starting with this one (found in 2 satellites will narrowly avoid colliding at 32,800 mph over Pittsburgh on Wednesday)
1/ We are monitoring a close approach event involving IRAS (13777), the decommissioned space telescope launched in 1983, and GGSE-4 (2828), an experimental US payload launched in 1967.
LeoLabs mentions a predicted conjunction of two defunct satellites with a worrisome separation
2/ On Jan 29 at 23:39:35 UTC, these two objects will pass close by one another at a relative velocity of 14.7 km/s (900km directly above Pittsburgh, PA). Our latest metrics on the event show a predicted miss distance of between 15-30 meters.
The image from one of the tweets is shown below. In addition to the two trajectories intersecting over the northeast US (Pittsburgh, PA) there is a highly elongated arc over Baja California, northwest Mexico and Texas of concentric narrow ellipses labeled "MSR".
Question: What does "MSR" represent in the context of this predicted conjunction? Is it related to the conjunction itself? If so, why is it shown so far away from the intersection of the two trajectories?