Infrastructure

Facilities

Benches built in house to reproduce on the ground the conditions a system will face in orbit, magnetic field, solar illumination and relative motion, with an independent measurement of ground truth, and the ground station for operations.

CubeDyna

A CubeSat attitude dynamics facility: an air bearing platform inside a Helmholtz cage, with simulated solar illumination and Earth albedo.

The Helmholtz cage generates a controlled magnetic field around the model, so magnetic actuators work as they would in orbit. The platform floats on an air bearing and is free to rotate almost without friction, carrying an inertial unit, reaction wheels, battery and microcontroller, plus an automatic mass balancing system. An independent reference system measures true attitude, a sun simulator and an albedo lamp reproduce the illumination, and a safety structure with a net protects the model. The facility is also used for teaching activities shared with other universities.

Magnetic field

gabbia di Helmholtz triassiale

Platform

cuscino d'aria, 3 assi

Balancing

automatico, masse mobili

Illumination

simulatore solare e lampada albedo

Ground truth

sistema di misura indipendente

Robotic testbed

Physically reproduces the relative motion between two satellites in proximity, acquiring images in known and repeatable conditions instead of simulating them.

The arm carries either the camera or the satellite mockup inside a 4.4 x 2.0 x 2.2 m dark room, with a sun simulator. Optical tracking provides the true pose to compare the estimate against.

Degrees of freedom

8

Arm

6 assi 1.3 m, corsa 1.8 m

Ground truth

tracciamento ottico a 4 camere

Image motion compensation

A Forward Motion Compensation prototype: the sensor, not the optics, is translated in antiphase with the apparent motion of the scene.

In very low orbit the scene moves across the sensor during exposure and produces smear, which limits integration time and therefore signal to noise ratio. The bench mounts the sensor on a closed loop biaxial piezo stage and drives it with a sinusoidal profile, acquiring the image during the forward scan half cycle.

Stage travel

100 x 100 µm

Repeatability

10 nm

Tracking error

2.5 - 5 µm RMS a 3 Hz

Integration time gain

fino a 5x

Alma Mater Ground Station

The lab ground station, with a software defined radio transceiver, used for university satellite operations.

The UHF and S-band antennas sit on the same roof, in Forlì. In S-band a 3 metre mesh dish with a dual mode circular feed serves the downlink: the received signal passes through a cavity filter, a low noise amplifier and finally the software defined radio. The azimuth and elevation rotator points to a tenth of a degree, and the mission control room hosts up to three operators on separate workstations for tracking, radio handling and telecommand and telemetry archiving. Since the chain is software defined, protocol, modulation and frequency are reconfigured without touching the hardware.

Position

44.2005°N 12.0673°E, 32 m

QTH locator

JN64AE

Bands

UHF, S

S-band dish

3 m a rete, F/D 0.45

Gain at 2320 MHz

35.4 dBd

Beamwidth

3.2°

Noise figure

0.5 dB

Rotator

AZ/EL 360/180°, 0.1°

Radio

USRP N210, SBX 0.4-4.4 GHz

Control room

3 postazioni

Missions supported

AlmaSat-1, ESEO