Cassini Swarm

Orbiter ("Queen Bee")

 

The Cassini Swarm Orbiter, also known as the "Queen Bee," is the spacecraft responsible for carrying out the scientific mission to study Titan's atmosphere, weather, and surface topography.

 

Mission Tasks

 

Navigation: Follow a gravity-assisted trajectory from Earth to Titan, including periodic Trajectory Correction Maneuvers (TCMs).

 

Attitude and Articulation Control: The Queen Bee achieves 3-axis attitude and articulation control through a steerable main engine. Gyroscopic wheels are used to stabilize the orientation of the spacecraft to maintain alignment of its High Gain Antenna (HGA) with Earth, its RADAR illuminator with Titan, and its ranging and communications antennas with the swarm of Worker Drones.

 

CubeSat Delivery: Insert into Titan orbit a swarm of 15 CubeSat "Worker Drones" using the timed-delivery module (TDM).

 

Earth Communications: Maintain a communications link with Earth through the Deep Space Network (DSN) to enable critical mission command-and-control (C2) services, monitoring of spacecraft telemetry, and exfiltration of science mission data collected from Worker Drones.

 

Science Mission: Measure atmospheric content, rain distribution, and surface topography using interferometric synthetic aperature RADAR (IFSAR). Using distributed SAR allows higher resolution by exploiting the redundancy of having multiple "looks" at the same position in the atmosphere or on the surface from slightly different angles. The Queen Bee will illuminate the atmosphere and surface within its view using various radiating elements. The reflections will be measured by the Worker Drones, and the Queen Bee will handle post-processing of the data before sending it back to Earth for further analysis.

 

CubeSats ("Worker Drones")

 

Each CubeSat, also known as a "Worker Drone," carries scientific sensors in a standardized 3U form-factor. Worker Drones are not equipped with their own propulsion systems and therefore must rely on passive Attitude and Articulation Control Systems (AACS).

 

Mission Tasks

 

Attitude Stabilization: After orbit insertion from the timed-delivery module (TDM), each Worker Drone will extend a gravity-gradient boom in its longest dimension to enable attitude stabilization and orientation. This mechanism will orient the Worker Drone with is RADAR antenna pointing toward Titan's surface and its ranging radio and communications antennas roughly coplanar with its neighbors and the Queen Bee in the azimuthal direction.

 

Antenna Extension: Spring-loaded mechanical devices in each Worker Drone will extend a communications antenna and an UWB ranging antenna from compartments housed within its body.

 

Ranging: Each Worker Drone uses an ultra-wideband (UWB) ranging radio to measure the distance between itself and its neighboring Worker Drones. The Queen Bee collects ranging estimates from each Worker Drone and then calculates precise position estimates of each probe.

 

Science Mission: The instruments on each Worker Drone measure the reflections of the Queen Bee's RADAR pulses as they arrive from Titan's atmosphere or surface. The captured data are uploaded to the Queen Bee for post-processing.