Rocket Lab launched an Electron rocket carrying one iQPS “Acadia” synthetic aperture imaging radar satellite to a 575 km circular low Earth orbit at 42° inclination on 2023-12-15 at 04:00 UTC. The launch was from Rocket Lab’s Launch Complex-1B on the Māhia Peninsula of New Zealand. This was the 42nd overall launch of the Electron rocket and the 9th of 2023. Payload mass is around 100 kg. This was the return to flight mission for the Electron launcher, which failed on its previous launch attempt on 2023-09-19 due to electrical arcing that prevented the second stage from firing.
I have cued the launch replay to start one minute before liftoff; scroll back if you like to see information about the rocket and payload and pre-launch preparations.
Here is a post-flight recap from Everyday Astronaut .
This launch was completely successful, and Rocket Lab and Electron appear to be back in business for future scheduled launches. No attempt was made to recover the first stage booster in this flight.
This got me wondering just how many channels of data from how many sensors are broadcast from a typical modern rocket? How does this compare to those in the first generation of rocketry?
Early rockets had a severely limited number of telemetry channels. The V-2 had a system which allowed monitoring only four parameters, and Wernher von Braun said it was so unreliable and limited it was rarely of use in diagnosing problems. In the postwar era, the most common systems involved a commutator (motor-driven circular switch) which allowed a number of analogue sensor signals to be multiplexed onto a single radio channel. This allowed dozens of signals to be sent, but the actual number of channels was often limited by the weight of the sensors and wiring to connect them to the telemetry transmitter. Often something would go wrong where there no sensor to monitor it and they had to add sensors to try to track it down and keep testing until they figured out what happened.
Digital signal processing and data communications and the adoption of microwave downlinks have made the amount of data that can be transmitted from a rocket essentially unlimited—many launchers now send live video feeds from multiple on-board cameras, which send thousands of times the data as Apollo era telemetry. Telemetry with hundreds of channels is now commonplace (consider: if you only monitor three parameters from each of the 33 engines in a Super Heavy booster, you’re already up to 99), and the constraint once again is the weight of the sensors (and the risk of possible failure modes induced by the sensors themselves) and connections, although adoption of network protocols to connect sensors has reduced the penalty compared to running separate wires for each.
In the case of the recent Rocket Lab launch failure, they did not have telemetry that allowed direct diagnosis of the electrical arc they decided was the cause of the failure. They drew the conclusion about the cause from information they did monitor, such as battery voltage and current on the second stage and the pressure of the atmosphere at the altitude where the stage was operating.