|Country of origin||United States|
|Applications||Launch service provider|
|Payload capacity||170 kg (370 lb)|
|Equipment||S band payloads|
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 including working with a number of potential customer with significant interest from government agencies. The first few Photon satellites would be technology demonstrators before transitioning to operational launches for customers, likely starting with NASA's CAPSTONE cubesat.
Photon is manufactured at Rocket Labs factory in Huntington Beach, California. It uses the Curie engine and 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 (370 lb). The low Earth orbit version of Photon can take 130 kg (290 lb) to Sun-synchronous orbit.
A modified version of Photon would have bigger propellant tanks and the HyperCurie engine for interplanetary missions. The interplanetary version will have a 40 kg (88 lb) payload capacity. HyperCurie is an evolution of the Curie engine, which comes in a monopropellent version and a bipropellant version, while the HyperCurie is a hypergolic version. HyperCurie is electrically pumped.
The first satellite to test the architecture was Electron Kick Stage Rocket Body/Photon Pathfinder  (COSPAR ID 2020-037F). It was launched aboard an Electron rocket on 13 June 2020 on its 12th Electron mission, "Don't stop me now" as its kickstage. It aimed to extend the function of the kick stage to enable it to function as a satellite in its own right.
Formally 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 First Light standalone mission is to demonstrate the new (as compared to "plain" kick stage) systems for operating in orbit as a long-duration standalone satellite. To demonstrate Photon bus' payload hosting, the 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 will first deliver customer satellites to orbit for transitioning into its own satellite operations. Pathstone operations are aimed at building flight heritage and focused on testing systems in preparation for launching NASA's CAPSTONE smallsat mission, later in 2021. These tests will include power and thermal management, attitude control via reaction wheels and communications systems.
The first operational launch for Photon will be NASA's CAPSTONE smallsat mission. Photon will deliver CAPSTONE on a trans-lunar injection burn to a near-rectilinear halo orbit.[when?] After completing all the mission requirements for NASA, Rocket Lab hopes to utilise its Photon spacecraft for a low-altitude lunar flyby. Qualification of the Photon kick stage for this mission was underway by December 2020.
13 June 2020, Photon Pathfinder, The Photon Pathfinder is the same space object as the Electron Kick Stage Rocket Body, essentially extending the function of the third stage so that it may act as a satellite in its own right. (Registered as a Photon bus)