On December 7 at 10:19 UTC, a United Launch Alliance (ULA) Atlas V 551 launched from SLC-41 at Cape Canaveral Space Force Station carrying the STP-3 mission for the U.S. Space Force.

Before we chat about the payloads, I’m going to nerd out about the rocket for a second; it’s cool. 

You might be interested to learn that the Atlas V on this mission incorporated several improvements, mainly for ULA’s future rocket, the Vulcan Centaur. The most significant improvement was a new fairing fabrication technique called Out of Autoclave, to make fairings faster and cheaper. As for the Centaur upper stage, it has two new systems: one which uses GPS to improve its already excellent orbital insertion accuracy and another system to keep the spacecraft batteries fully charged throughout the long mission.

Now, on to the many payloads!

STPSat-6 carries several experimental payloads for the Space Force, NASA, and the National Nuclear Security Administration. NASA’s payload is the Laser Communication Relay Demonstration (LCRD) which will “test technologies for the next generation of data relay satellites”. 

Laser communications have been tested in space for decades and have worked as far as 24 million miles from Earth on NASA’s MESSENGER spacecraft. Compared to radio waves, laser communications have much higher bandwidth, often in the range of one billion bits, or gigabit, per second, or higher. LCRD is a relay only, meaning that it can’t transmit data to other satellites; it can only transmit and receive data to ground stations. Currently, it will only be able to send data to two mountain-top ground stations: one on Haleakalā in Hawaii and the other in California. Once a laser terminal is installed on the International Space Station (ISS), LCRD will be able to receive data from the ISS and retransmit that data to the ground.

The military payloads include one which will track nuclear detonations in space and in the atmosphere. Other payloads are for space weather while others are intended to assess the physical environment around the spacecraft, including how many objects might be nearby, what those objects are, and how those other objects may move, among other details.

One of the payloads, the LDPE-1 which stands for Long Duration Propulsive Evolved Expendable Launch Vehicle Secondary Payload Adapter, carried other payloads. It’s essentially a metal ring normally used to attach smaller satellites below the main satellite on the same rocket, turned into a satellite in its own right with power and propulsion. None of those payloads were disclosed, though it was described as being capable of a one- to three-year mission carrying experimental payloads for “rapid risk reduction efforts to inform future programs”.

More Information

NASA’s Laser Communications Relay Demonstration: 6 Things You Need to Know (NASA)

Launch video