posted 01-28-2020 07:48 AM               

We are monitoring a close approach event involving IRAS (13777), the decommissioned space telescope launched in 1983, and GGSE-4 (2828), an experimental U.S. payload launched in 1967.

On Jan. 29 [2020] at 23:39:35 UTC, these two objects will pass close by one another at a relative velocity of 14.7 km/s (900 km directly above Pittsburgh, Pennsylvania). Our latest metrics on the event show a predicted miss distance of between 15-30 meters [50 to 100 feet].

These numbers are especially alarming considering the size of IRAS at 3.6 m x 3.24 m x 2.05 m [11.8 x 10.6 x 6.7 feet]. The combined size of both objects increases the computed probability of a collision, which remains near 1 in 100.

Events like this highlight the need for responsible, timely deorbiting of satellites for space sustainability moving forward. We will continue to monitor this event through the coming days and provide updates as available.

Here is an interactive visualization of this event based on our most recent data. Click "Jump to TCA" to see how close these objects should pass to one another.

The Infrared Astronomical Satellite, or IRAS, was the first mission to put a telescope in space to survey the sky in infrared. The telescope exhausted its cryogen and ceased operation on Nov. 21, 1983.

posted 01-28-2020 06:10 PM               

Our latest data on the IRAS/GGSE 4 event shows potential miss distances of 13-87 meters, with a lowered collision probability currently at 1 in 1000. Time of closest approach remains at 2020-01-29 23:39:35.707 UTC.

posted 01-29-2020 10:29 AM               

Our latest update this morning for IRAS/GGSE 4 shows a 12 meter miss distance, with a Probability of Collision (Pc) back to 1 in 100.

Since we learned that GGSE 4 has a deployed 18 meter boom and we do not know which direction it is facing relative to IRAS, this changes the assumptions used in computing collision risk.

Adjusting our calculations to account for larger object sizes (by increasing our combined Hard Body Radius from 5m to 10m), this yields an updated collision probability closer to 1 in 20.

Though it is still unlikely that these objects will collide, we have tasked our radars to schedule longer duration tracking on both objects following the event to search for evidence of any new debris (and hopefully not find any!)

posted 01-29-2020 07:52 PM               

18 Space Control Squadron (18 SPCS) confirmed the two inactive satellites (IRSA and GGSE-4) crossed paths without incident.