Introduction

VESICOLOS is a small fluorescence microscope in a 2U CubeSat unit, designed for the flight on the sounding rocket MAPHEUS®. It is a sub-payload of the MOSAIC module, which handles power and signals for its CubeSat-sized inserts.

The setup was designed for the observation of giant unilamellar vesicles (GUV) in microgravity, hence the name.

The MAPHEUS sounding rocket is a program run by the German Aerospace Center (DLR), in collaboration between the Institute of Frontier Materials on Earth an in Space, the Institute of Aerospace Medicine, and the Mobile Rocket Base MORABA. VESICOLOS is part of a collaboration between DLR and the University of Bordeaux.

Contributors

VESICOLOS was created by

• Jörg Drescher - hardware engineering (DLR-FM)
• Jens Hauslage - optics (DLR-ME)
• Thomas Voigtmann - software (DLR-FM)
• Laura Alvarez - science (U Bordeaux)
• Paulina Blair - science (DLR-FM / U Düsseldorf)
• Christian Kahlo - software revision, spare parts (VX4)

Hardware Setup

For the MAPHEUS-16 flight, we used a Raspberry 5, and the following hardware setup:

• Temperature sensor on SPI, 2-wire setup using Adafruit MAX31865 board.
• LED and Heater on PWM channels.
• Servo motors Waveshare ST3020 controlled by a Waveshare driver.
  • Stage movement (X/Y): 2.3mm per turn of 4096 steps
  • Focus movement (Z): 0.1mm per turn of 4096 steps

Raspberry GPIO pin layout (using GPIO numbers, not physical pin numbers):

GPIO	Function	Remark
GPIO 5	SPI CS1	temperature sensor
GPIO 6	SPI CS2	not yet connected on the clip connector
GPIO 9	SPI MISO	standard
GPIO 10	SPI MOSI	standard
GPIO 11	SPI CLK	standard
GPIO 12	PWM1	LED
GPIO 13	PWM2	heater
GPIO 17	LO	lift off from MOSAIC
GPIO 23	mug	microgravity detection from MOSAIC

Raspberry Configuration

• Make sure it boots into graphical desktop, using LXDE
• The /boot/firmware/config.txt should have the following entries:

  usb_max_current_enable=1
  dtparam=uart0=on
  dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4
  dtoverlay=w1-gpio
  dtoverlay=disable-wifi
  dtoverlay=disable-bt

  These should have the effect that UART is enabled, 2 hardware PWM channels are enabled, and WiFi is off. Also the Raspberry 5 should be forced to ignore the underpower warning if it thinks that our power supply cannot handle 5V/5A (it can).
• The EEPROM config should be adapted with the rpi-eeprom-config tool. The flight configuration (MAPHEUS-16) was

  BOOT_UART=1
  BOOT_ORDER=0xf461
  NET_INSTALL_AT_POWER_ON=0
  PSU_MAX_CURRENT=5000

Software Installation

The contents of this repository should be placed into ~/Desktop/vesicolos such that the script ~/Desktop/vesicolos/start.sh can be found.

Inside this folder, a python virtual environment needs to be created as follows:

python3 -m venv --system-site-packages venv
. venv/bin/activate

Then install the required python libraries found in requirements.txt. For the lgpio library on the Raspberry 5, we found it necessary to first install lg from https://abyz.me.uk/lg/download.html (follow instructions there). The important packages that do not come with the raspberry install should be

adafruit-circuitpython-max31865 gpiozero lgpio rpi-lgpio pyserial

The file in autostart needs to be copied into ~/.config/autostart/. This should make the vesicolos python program automatically start once the LXDE desktop is up.