The array.
The Luminoth security sensor array is a Luminoth device used to transmit data. During their war with the Ing, it appears that devices such as these were compromised by the enemy for their own use, likely during the time when the "machines" went rogue and joined the horde.
One of these devices is located in the Transport to Temple Grounds within the Sanctuary Fortress. It is possible that the Ing and the rogue machines used this to detect Samus as she first entered the region, as well as detect the Space Pirates that arrived before her.
Scan
"Object analysis complete. This is a Luminoth security sensor array. Array is online and transmitting data. Datafeed appears to be compromised, however. It is possible that the enemy is using this array."