Detumbling

Objectives

ArcticSat detumbling analysis was performed using the ArcticSat attitude simulator. The objectives of this analysis include:

1. The total duration of a complete detumbling maneuver from deployment (R-ARC-ADC-021).

2. The total power consumption of the detumbling maneuver.

3. Identify potential anomalies to be analyzed further in flight software(R-ARC-ADC-026).

4. Test transition to sun-pointing after successfully detumbling (R-ARC-ADC-035).

Simulation Setup

As a result, the simulation was set up to represent a worst-case scenario for the metrics we are investigating. ArcticSat will deploy from a 4U EXOpod Nova. Exolaunch reports tip-off rates for all deployments stay below than 10 deg/s in all axes, but 3U CubeSats tend to be more stable. Based on this, initial body rates were chosen to be 6 deg/s in the x- and z-axes in the body frame, and 2 deg/s in the y-axis. 

ArcticSat will have the least power generation capability around the summer solstice, when it spends the most time in eclipse, so this deployment time was chosen to investigate. Time and orbit details can be found below.

• Epoch: 21 June 2025 12:00:00 UTC

• Altitude: 525 km

• Inclination: 97.5 deg

• RAAN: 180 deg

• Arg. Perigee: 0 deg

• True Anomaly: 0 deg

Controllers

Detumbling mode uses a B-dot controller which calculates a filtered derivative of the magnetic field and commands a torque in the opposite direction using ArcticSat's magnetorquers. The only sensors used are the magnetometer and gyroscope, and the only actuators used are the magnetorquers. Control commands operate on a 70% second duty cycle (the magnetorquers are activated for 0.7 seconds out of every second) to give the magnetometer time to collect data for the derivative calculation.

Simulation Results

The results of this simulation show that ArcticSat successfully detumbles after about 80 minutes, which satisfies R-ARC-ADC-021. The total depth of discharge on the battery after detumbling was found to be approximately 6%.

It can be seen around 3000 seconds in the body rate plot that the spacecraft seems to come to a constant, low spin rate before entering more of an unstable spin, then returning to another constant rate approaching 5000 seconds. This anomaly should be analyzed and tested on flight hardware as per R-ARC-ADC-026.