Rocket Lab Photon

Photon is a satellite bus based on Rocket Lab's kick stage.



It was designed to be highly customizable to serve a variety of uses including LEO payload hosting, lunar flybys, and interplanetary missions.

Photon uses chemical propulsion for orbit adjustments, utilizing a range of engines such as Rocket Lab's own Curie or HyperCurie, or other third party engines.

Photon first launched in August 2020 on Rocket Lab's I Can't Believe It's Not Optical mission, where it served as a pathfinder, and has since flown three more times. It also flew the CAPSTONE mission.

In an upcoming mission, two Photon satellite buses will be used to observe the Martian magnetosphere. Another Photon will serve as the transfer stage to the joint Rocket Lab-MIT Venus Life Finder atmospheric probe.

Development
In April 2019, Rocket Lab announced plans to create a new satellite bus, named Photon, to launch small payloads into Earth orbit. Its goal was to reduce the complexity and development time for customers, enabling technology demonstrations without the complexity of developing a full spacecraft. At the same time the company was aiming to broaden its portfolio and diversify its revenue streams. In October 2019, it announced that it aimed to launch its first mission as soon as the fourth quarter of 2020. The company also announced it was targeting lunar orbit as part of its services offered with Photon, enabled by a new bi-propellant propulsion system. The development of Photon included working with a number of potential customers, with significant interest from government agencies. The first few Photon satellites would be technology demonstrators before transitioning to operational launches for customers, which started with NASA's CAPSTONE cubesat in June 2022.

Rocket Lab is planning to launch Photon to Venus in December 2025, delivering a laser-tunable mass spectrometer into the Venusian atmosphere.

Design
Photon is manufactured at Rocket Lab's factory in Huntington Beach, California. It can utilize a variety of engines, including those developed by Rocket Lab itself, such as the Curie and HyperCurie engines, as well as engines from third-party sources, such as the one powering the EscaPADE mission. Photon communicates on S-band. Depending on the orbital inclination (37° to Sun-synchronous orbit), it is expected to have a maximum payload capacity of 170 kg. The low Earth orbit version of Photon can take 130 kg to Sun-synchronous orbit.

A modified version of Photon has bigger propellant tanks and the HyperCurie engine for interplanetary missions. The interplanetary version has a 40 kg payload capacity. HyperCurie is an evolution of the Curie engine, which comes in a monopropellant version and a bipropellant version, while the HyperCurie is a hypergolic version. HyperCurie is electrically pumped.

Initial launches
The inaugural Photon satellite was the Photon Pathfinder/First Light satellite (COSPAR ID 2020-060A) described by Rocket Lab as its "first in-house designed and built Photon demonstration satellite". It was launched aboard Electron rocket on 31 August 2020 on the 14th Electron mission "I Can't Believe It's Not Optical". First Light had a dual role in the mission: first as the final rocket stage delivering the customer satellite (Capella 2) and then as a standalone satellite undertaking its own orbital mission. The purpose of the First Light standalone mission was to demonstrate the new (as compared to "plain" kick stage) systems for operating in orbit as a long-duration standalone satellite. To demonstrate Photon's payload hosting capabilities, First Light had a low-resolution video camera.

The second formal test, Photon Pathstone, was launched on 22 March 2021 on the 19th Electron mission "They Go Up So Fast". Like First Light, Pathstone first delivered customer satellites to orbit before transitioning into its own satellite operations. Pathstone operations were aimed at building flight heritage and focused on testing systems in preparation for launching NASA's CAPSTONE smallsat mission in June 2022. These tests included power and thermal management, attitude control via reaction wheels and communications systems.

The first operational launch for Photon was NASA's CAPSTONE smallsat mission. Qualification of the Photon kick stage for this mission was underway by December 2020. Photon delivered CAPSTONE on a trans-lunar injection (TLI) burn on 6th day from liftoff after performing 6 apogee raising burns at perigee within every 24 hours from liftoff, leading to TLI and a near-rectilinear halo orbit. After this the CAPSTONE was deployed in its journey to the Moon.

After completing all the mission requirements for NASA, Rocket Lab utilised its Photon spacecraft for a low-altitude lunar flyby.

Photon versions
Due to the high amount of customization Photon can undergo, Rocket Lab decided to rebrand Photon and split it into different spacecraft: Explorer, Lightning, Pioneer, and Photon.

Explorer
Explorer is a high delta-V spacecraft designed for deep space missions. The first Explorer flew in 2022 and delivered CAPSTONE to a trajectory towards the Moon. Currently, two Explorers are being built for the EscaPADE mission. Explorer can be launched on any rocket, depending on the mission profile.

Lightning
Lightning is designed for LEO constellations and is intended to operate for 12+ years in LEO. It boasts a 3 kW power delivery system and is suited for high-duty-cycle telecommunications and remote sensing. Lightning currently has no flight heritage, with the first launch planned for 2025. Both the satellites (buses) for Globalstar and the Space Development Agency are based on the Lightning architecture.

Pioneer
Pioneer is a highly specialized satellite bus designed to support payloads up to 120 kg for special missions, including re-entry and dynamic space operations. Pioneer first took flight in 2023, supporting a mission for Varda Space Industries where the capsule atop the bus grew crystals of the drug ritonavir. After growing the crystals and experiencing some regulatory hold-ups, the spacecraft returned to Earth and landed in Utah.

Photon
Photon is the upgraded version of Rocket Lab's kick stage. It features power, propulsion, and communications systems for delivering payloads to LEO. The first Photon was launched in 2020, deploying a satellite for Capella Space. After deployment, the Photon spacecraft served as a pathfinder.

Upcoming missions
Confirmed upcoming missions for Photon and Photon variants.