Flock-1 CubeSat Constellation begins Deployment from Space Station
ISS Expedition 38
The Flock-1 constellation of Cube-Satellites has begun deployment from the International Space Station. Flock-1, operated by Planet Labs Inc. of San Francisco, consists of a total of 28 satellites that will provide high resolution images of Earth for a number of purposes. Using the Japanese Robotic Arm and a deployment system provided by NanoRacks, the first set of satellites was released on Tuesday. More deployments will come over the coming days and weeks to establish a constellation of CubeSats with a close eye on planet Earth.
The hardware needed for the satellite deployments, including the CubeSats, was flown to ISS aboard the Cygnus Orb-1 mission that blasted off in January. After arriving at ISS, Cygnus was unloaded and the CubeSat hardware was moved to the Kibo module. In charge of CubeSat preparations and deployments is Japanese Astronaut and robotics specialist Koichi Wakata. Over the past weeks, Wakata prepared the CubeSat deployment system for the Flock-1 satellites. The dispenser holds up to sixteen three-unit CubeSats and is attached to the Multi-Purpose Experiment Platform (MPEP) that can be grappled by the Japanese Remote Manipulator System and deploy the satellites in pairs upon command issued from inside ISS or the JAXA Control Center in Tsukuba, Japan.
Originally, the first deployment of the Flock-1 CubeSats was planned last Thursday, but during preparations, Wakata ran into some minor trouble with cross threaded bolts and fasteners that prevented the installation of the MPEP electronics box. Specialists on the ground looked at the problem and instructed Wakata to install the box in an alternate location on the MPEP. With the MPEP and NanoRacks CubeSat Deployers (NRCSDs) integrated, the system was placed inside the airlock of the Japanese Kibo module. The Airlock's slide table was used to move the system outside and place it within the reach of the Japanese robotic arm. Once grappled, the deployer was moved to the correct orientation for the release of the satellites into a precisely calculated trajectory to avoid re-contact with ISS.
On Tuesday, after final checks, the command to deploy the first two satellites was sent at around 8:20 UTC, but there was no deployment. JAXA Flight Controllers reconfigured the system and again sent the deployment command at 8:33 UTC. This time, the system responded as planned and released the first pair of Flock-1 satellites. With the first two satellites on their way, teams prepared the next deployment which occurred at around 12:41 UTC. As the small satellites floated away from ISS, Koichi Wakata acquired photos of the CubeSats. On a typical day, three or four CubeSat deployments are expected.
NanoRacks CubeSat Deployers (NRCSDs) integrated on MPEP
The deployments are performed with intervals of several hours to create spacing in between the satellites that are expected to remain in orbit for over one year.
Flock-1 satellites Pre-Launch
Dove-2 Satellite Image
Once the first 16 Flock-1 satellites are released, the deployer will be taken back inside ISS and the final 12 satellites will be prepared for release later this month along with five scientific and student-built CubeSats that are also awaiting deployment.
Flock-1 represents 28 three-unit CubeSats operated by Planet Labs to build an Earth-observation constellation based on CubeSats. The technology and infrastructure for this program was demonstrated by four Dove satellites that were launched in 2013 and collected images of Earth to test the capabilities of the system and prepare for the operation of a large constellation of satellites.
The spacecraft are based on the three-unit CubeSat specification having a launch mass of about 5 Kilograms and being 100mm × 100mm × 340mm in size featuring body mounted solar panels and two deployable solar arrays with three panels each. The solar arrays are spring-loaded and deployed by burn-wires. Flock spacecraft contain batteries that provide power to the various systems. The load bearing satellite structure consists of three skeleton plates, with L rails along each corner edge.
Attitude data is provided by three-axis magnetometers to accomplish three-axis stabilization via magnetic torquers.
The main payload of each satellite is an optical telescope of unknown specifications to acquire high-resolution images of Earth. The telescope is protected by an aperture cover that is deployed via springs. The optical axis is down the central axis of the satellite to achieve a maximum focal length. Imagery is downlinked via X-Band while commands to the spacecraft are uplinked via S-Band.
Deploying CubeSats from ISS has a number of benefits. Launching the vehicles aboard the logistics carrier of ISS visiting vehicle's reduces the vibration and loads they have to encounter during launch.In addition, they can be packed in protective materials so that the probability of CubeSat damage during launch is reduced significantly. Also, once arriving at the Space Station, the satellites can be checked pre-deployment, making sure any damage is detected before committing them to flight.