Deep Purple telescope is one step closer to launch

In January 2024, Lawrence Livermore National Laboratory’s (LLNL) space hardware team completed the qualification of the Deep Purple payload. This payload is set to be aboard NASA’s Pathfinder Technology Demonstrator-R (PTD-R) satellite, scheduled for launch this summer. Once operational, Deep Purple will observe ultraviolet (UV) and short-wave infrared (SWIR) light. (Photos: Garry McLeod)

The LLNL team developed Deep Purple, an optical payload featuring a new design for a monolithic UV and SWIR telescope. This mission will be the first to demonstrate simultaneous monolithic UV and SWIR optical sensing from space using two co-boresighted, 85 mm aperture monolithic telescopes. The system employs a compact custom electronics module and a lightweight carbon-composite optical housing and radiator, opening new avenues for scientific observations and real-time space domain awareness.

LLNL delivers Deep Purple telescope, the compact dual-band telescope for launch this summer

The satellite is set to launch this summer on SpaceX’s Transporter-11 mission from Vandenberg Space Force Base in California. SEOPS, the rideshare provider, managed the integration and mission services for the spacecraft.

Developed and delivered in roughly one year for less than $1 million, the Deep Purple telescope will observe UV and SWIR light from high-UV stars and the galactic bulge. LLNL’s monolithic optics are compact Cassegrain telescopes made from a single piece of fused silica. This design ensures a compact, shelf-stable, and resilient space telescope capable of enduring the harsh conditions of rocket launch and outer space.

"The optical package is highly configurable, allowing us to mix and match different sensors and optics within the same infrastructure to meet various mission needs using a standardized small-satellite bus," explained Jordan Smilo, the principal investigator for Deep Purple and the lead mechanical engineer for LLNL’s space hardware.

"Deep Purple exemplifies how LLNL’s Space Program combines R&D with the deployment of innovative technology to support its national-security mission. Each satellite offers an opportunity for development and flight heritage to meet the nation’s increasing need for responsive payloads," Smilo added.

The Deep Purple payload, including its dual optical module and electronics, is housed in a 25 cm x 15 cm x 10 cm package. "We believe Deep Purple will be the smallest space telescope providing both SWIR and UV imaging in space," noted John Ganino, associate program leader for space hardware at LLNL and the system engineer lead for Deep Purple.

"This satellite is a 6U-sized space vehicle, equivalent to the volume of six 10-centimeter CubeSats. The size and mass constraints for Deep Purple were stringent, with a maximum weight limit of 5 kilograms (about 11 pounds). Incorporating our own electronics control module within the same volume was an additional challenge," Smilo stated.

To meet these requirements, the team redesigned the electronics module to fit precisely within the available space adjacent to the optics. "We replaced the heavier invar material, typically used for optical housings, with a novel, lightweight, carbon-fiber-nano-tube-composite housing. This significantly reduced the satellite’s weight and cost while maintaining optical performance. We met the maximum mass for our entire payload with margin," Smilo explained.

Deep Purple, the smallest space telescope for SWIR and UV imaging

Once operational, Deep Purple will simultaneously observe UV and SWIR light from high-UV stars and the Milky Way’s galactic bulge. This capability enables the observation of time-domain astronomical events, such as Fast Blue Optical Transients (FBOTs), a recently discovered and not yet fully understood phenomenon. Deep Purple will also attempt to demonstrate real-time space domain awareness using these unique sensing bands. LLNL’s Space Program continues to showcase its leadership in developing and delivering small satellite tools and capabilities.

"Deep Purple, though small - not much bigger than a loaf of bread - could significantly impact space-domain awareness. The team’s ability to deliver such a remarkable tool in a short amount of time, while meeting NASA’s rigorous requirements, is another impressive achievement for LLNL’s space program. Our list of achievements continues to grow. It’s an exciting time," commented Ben Bahney, program leader for the space program at LLNL.

NASA’s Small Spacecraft Technology program, based at NASA’s Ames Research Center in California’s Silicon Valley and within the agency’s Space Technology Mission Directorate in Washington, funds and manages the PTD-R project.