SeaLion Mission Architecture

Stakeholder Needs

The SeaLion Mission Architecture is guided by a series of stakeholder needs, listed below.

1.1: Primary Mission Objective A1

The SeaLion mission shall establish UHF communication link with Virginia ground station

1.2: Primary Mission Objective A2

The SeaLion mission shall establish S-Band communication link with MC3 ground station

1.3: Primary Mission Objective A3

The SeaLion mission shall successfully transmit “mission data” defined above to ground stations on the Earth.

1.4: Primary Mission Objective A4

The SeaLion mission shall adhere to CubeSat standards.

Reference:

CubeSat Design Specification Rev. 13

1.5: Primary Mission Objective A5

The SeaLion mission shall validate the operation of the Impedance Probe (IP) as a primary payload in-orbit.

2.1: Secondary Mission Objective B1

The SeaLion mission shall provide a means to validate a Multi-spectral Sensor (Ms-S) in-orbit

2.2: Secondary Mission Objective B2

The SeaLion mission shall provide a means to validate a deployable composite structure (DeCS) in-orbit

3.1: Tertiary Mission Objective C1

The SeaLion mission shall qualify on-orbit the deployment and functioning of the newly developed UHF antenna system and its deployment.

3.2: Tertiary Mission Objective C2

The SeaLion mission shall qualify a CubeSat bus architecture for very-low Earth orbit (VLEO)

3.3: Tertiary Mission Objective C3

The SeaLion shall verify DeCS in-orbit behavior performance.

Stakeholder Needs Mapping

User Stories

The SeaLion Mission Architecture’s stakeholder needs are then used to identify a series of user stories which then lead to design decisions captured in data structure and activity definitions.

1: Ping Satellite

As a Ground Station Operator I want to Ping satellite so that I can Establish communication link with satellite.

Example:

Ping the satellite in order to establish UHF communication link with Virginia ground station

Derived From:

Primary Mission Objective A1

2: View Satellite Beacon Data

As a Ground Station Operator I want to view satellite beacon data (alternating between health & mission data), received via UHF so that I can verify that satellite is operating nominally.

Example:

View satellite beacon data (health or mission data) to verify that state vector correspond with expected orbit profile and/or to validate that a mission mode was successful

3: Send Request to Set Interrupt Timer

As a Ground Station Operator I want to send a request to set count value at which interrupt timers (i.e., beacon, GPS ping, or orbit propagator) are triggered so that I can finetune parameters for attitude or orbit analysis or to conserve power.

Example:

Update beacon rate to transmit every 30 minutes to conserve power

4: Request Telemetry or EventLog Data

As a Ground Station Operator I want to Request satellite telemetry or eventlog data so that I can verify/validate health status or mission data.

Example:

Request satellite telemetry packets for local verification/validation of onboard AODS computations

4.1: Request Satellite Health Data

As a Ground Station Operator I want to request satellite health data packet so that I can verify/validate AODS sensors & GPS data are within nominal parameters.

Example:

Request satellite health data packet to verify or validate state vector corresponding to expected orbit profile based on pre-computed orbit propagation model

Derived From:

Request Telemetry or EventLog Data

4.1.1: Request Satellite Health Data via S-Band Radio

As a Ground Station Operator I want to request satellite health data packet via S-band radio so that I can verify/validate AODS sensors & GPS data are within nominal parameters.

Example:

Request satellite health data packet via S-band radio to verify or validate state vector corresponding to expected orbit profile based on pre-computed orbit propagation model

Derived From:

Request Telemetry or EventLog Data
Primary Mission Objective A2

4.2: Request Satellite Mission Data

As a Ground Station Operator I want to request satellite mission data so that I can validate in-orbit AODS and/or payload performance.

Example:

Request satellite mission data to verify that state vector & AODS sensor data correspond with expected orbit profile and/or validate that a mission mode was successful

Derived From:

Request Telemetry or EventLog Data
Primary Mission Objective A1
Primary Mission Objective A3
Primary Mission Objective A5
Secondary Mission Objective B1
Secondary Mission Objective B2
Tertiary Mission Objective C1
Tertiary Mission Objective C2
Tertiary Mission Objective C3

5: Send Request to Set Mission Mode Duration

As a Ground Station Operator I want to send a request to set mission mode duration so that I can manage time spent per mission mode.

Example:

send a request to set Mission Mode 1 duration to 25 minutes

User Stories Mapping

User stories as Use Case Diagram

Data Structures

This section covers each data structure type in the SeaLion Mission Architecture.

Satellite Health Data Packet

Purpose: Data structure for satellite health data packet used for beacon telemetry

Satellite Health Data Packet Template

call_sign: {{call_sign}}
battery_health: {{battery_health}}
temperature_battery: {{temperature_battery}}
mode: {{mode}}
state_vector: {{state_vector}}

Table 1. Satellite Health Data Packet Specification
Field	Type	Description
call_sign	string	Identifying call sign for the Sealion mission.
battery_health	float	Percent value indicating the remaining charge of the batteries.
temperature_battery	float	The temperature of the battery. Units in Kelvin.
mode	integer	Integer value indicating current mission mode. 0 = Safe, 1 = mission mode 1, 2 = mission mode 2, 3 = mission mode 3.
state_vector	ECIStateVector	ECI state vector from orbit propogator at time of beacon.

Derived From:

View Satellite Beacon Data
Request Satellite Health Data

Satellite GPS Data

Purpose: Data structure for GPS data used for orbit propagation

Satellite GPS Data Template

time_stamp: {{time_stamp}}
altitude_data_GPS: {{altitude_data}}
lattitude_GPS: {{lattitude}}
longitude_GPS: {{longitude}}

Table 2. Satellite GPS Data Specification
Field	Type	Description
time_stamp	string	Time stamp when GPS data was acquired.
altitude_data_GPS	float	The altitude data of the satellite from GPS.
lattitude_GPS	float	Lattitude coordinate of the satellite from GPS.
longitude_GPS	float	Longitude coordinate of the satellite from GPS.

Satellite AODS Sensor Data

Purpose: Data structure for satellite AODS sensor data used for attitude determination or incremental orbit propogation

Satellite AODS Sensor Data Template

imu_gyro_x: {{imu_gyro_x}}
imu_gyro_y: {{imu_gyro_y}}
imu_gyro_z: {{imu_gyro_z}}
imu_magnetometer_x: {{imu_magnetometer_x}}
imu_magnetometer_y: {{imu_magnetometer_y}}
imu_magnetometer_z: {{imu_magnetometer_z}}
sun_sensor_pitch_pos: {{sun_sensor_pitch_pos}}
sun_sensor_pitch_neg: {{sun_sensor_pitch_neg}}
sun_sensor_yaw_pos: {{sun_sensor_yaw_pos}}
sun_sensor_yaw_neg: {{sun_sensor_yaw_neg}}
sun_sensor_roll_pos: {{sun_sensor_roll_pos}}
sun_sensor_roll_neg: {{sun_sensor_roll_neg}}
time_stamp: {{time_stamp}}

Table 3. Satellite AODS Sensor Data Specification
Field	Type	Description	Source
imu_gyro_x	float	The angular rate of the body with to respective to the x-axis in the IMU’s reference frame.
imu_gyro_y	float	The angular rate of the body with to respective to the y-axis in the IMU’s reference frame.
imu_gyro_z	float	The angular rate of the body with to respective to the z-axis in the IMU’s reference frame.
imu_magnetometer_x	float	The magnetic field strength with respective to the x-axis in the IMU’s reference frame.
imu_magnetometer_y	float	The magnetic field strength with respective to the y-axis in the IMU’s reference frame.
imu_magnetometer_z	float	The magnetic field strength with respective to the z-axis in the IMU’s reference frame.
sun_sensor_pitch_pos	float	Sun sensor measurement with respect to positive pitch angle.	[]
sun_sensor_pitch_neg	float	Sun sensor measurement with respect to negative pitch angle.	[]
sun_sensor_yaw_pos	float	Sun sensor measurement with respect to positive yaw angle.	[]
sun_sensor_yaw_neg	float	Sun sensor measurement with respect to negative yaw angle.	[]
sun_sensor_roll_pos	float	Sun sensor measurement with respect to positive roll angle.	[]
sun_sensor_roll_neg	float	Sun sensor measurement with respect to negative roll angle.	[]
time_stamp	string	Time stamp of the last transmission.

Derived From:

ECIStateVector

Purpose: Data structure for the earth-centered inertial (ECI) state vector in cartesian coordinates computed from GPS data or orbit propagator

ECIStateVector Template

x: {{x}}
y: {{y}}
z: {{z}}
xd: {{xd}}
yd: {{yd}}
zd: {{zd}}

Table 4. ECIStateVector Specification
Field	Type	Description
x	integer	position in kilometers (km) along x-axis
y	integer	position in kilometers (km) along y-axis
z	integer	position in kilometers (km) along z-axis
xd	integer	velocity in kilometers per second (km/s) along x-axis
yd	integer	velocity in kilometers per second (km/s) along y-axis
zd	integer	velocity in kilometers per second (km/s) along z-axis

Mission Data

Purpose: Defines EVR (event) elements to be recorded to the eventLog during a mission mode

Mission Data Template

entry_tle: {{entry_tle}}
obc_sensors: {{obc_sensors}}
mission_data: {{mission_data}}
exit_tle: {{exit_tle}}

Table 5. Mission Data Specification
Field	Type	Description
entry_tle	ECIStateVector	ECIStateVector at time of beginning of mission mode
obc_sensors	AODSSensorData	AODS Sensor data
mission_data	string	Data recorded during mission mode
exit_tle	ECIStateVector	ECIStateVector at time of end of mission mode

Derived From:

View Satellite Beacon Data
Request Satellite Mission Data

Data Structures Mapping

Finite State Machine