HENRY-1 Module for Collecting Stratospheric Microbes


Microbes that inhabit the upper atmosphere are of great interest due to the fact that they provide a good model for how life could persist and adapt in extreme, extraterrestrial environments. At high altitudes, bacteria are put under strains similar to those they would encounter on the Martian surface: high levels of radiation, desiccation, minimal oxygen, etc. Other implications of high altitude microbiology include transcontinental pathogen transport and impacts on weather patterns. However, little is known about the identity, quantity, and variety of microbes in the Earth’s upper atmosphere. This is largely owing to the difficulty inherent to studying this region. Sampling techniques are limited to aircraft, rocket, balloon, summit stations, and precipitation studies. Many successful studies of upper atmosphere microbial aerosol samples have been conducted using helium-filled latex weather balloons. The sampling payload is typically attached to the underside of the balloon. The HENRY-1 mission, lead by the East Bay Amateur Radio Club (EBARC) contains a prototype of a reusable, lightweight, low-budget device for collecting bio-aerosols at high altitudes. This payload contains an electronics unit as well a sampling chamber. The electronics are responsible for reading altitude information and operating the sampling chambers at the correct altitude. Based on this generic model, we have designed a compact, reusable system for sampling upper atmosphere bio-aerosols. The fidelity of microbial samples at high altitudes is predicated on the sterility of the collection system. A sampling module must be able to remain sterile before launch as well as after impacting the Earth. The HENRY-1 bio collection payload provides a design apparatus that can enable researchers on the ground to capture, culture, and identify bacteria found in the upper atmosphere.

In A Nutshell

This system captures bacteria on silicone-coated aluminum rods that are exposed to the upper atmosphere at a designated altitude. The system seals so that these bacterial samples can be collected when the balloon returns to Earth.

Previous and Ongoing Research

Significant microbiology research has been conducted using high altitude balloons. A few notable examples follow.

The NASA E-MIST project uses a balloon platform to expose microorganisms to the stratosphere.

The LAMB payload, developed by LSU researchers uses a similar system to capture upper atmosphere microbes.


The bio-collection module is composed of two main components: a large outer shell, and a small inner tube. The outer tube is made of 1″ PVC SCH-40 (SCH-40 denoting the thickness of the pipe walls) with a 1 1/4″ SCH-40 cap on one end. The inner tube is made of 3/4″ PVC SCH-40 with a 1″ SCH-40 cap on one end. The length of the outer tube is 23cm (with cap in place) and the length of the inner tube is 18cm (with cap in place). The caps are held in place by Clear PVC Cement (Methyl Ethyl Ketone, Cyclohexanone, Tetrahydrofuran) that was primed by PVC Purple Primer (Acetone, Cyclohexanone, Methyl Ethyl Ketone, Tetrahydrofuran). Note: these PVC glues contain volatile organic compounds (VOC) at concentrations around 500g/L.

PVC was chosen as the base-material due to its features:
-Completely impermeable to air, water.
-Shock resistant
-Low-cost, commercially accessible
-Ease of machining

SCH-40 PVC can be easily cut with a typical hacksaw or pipe cutter. A hacksaw, however, will leave small PVC particulates at the cuts. These should be wiped away and the junctions sanded so that they do not interfere with the PVC cement and create gaps in the pipe junctions.

Placing the small innertube inside the larger shell creates a closed system. The junction between the inner-tube cap and the outer-shell opening is closed with a rubber seal to prevent air inflow from bringing airborne contaminants inside the module during and after flight.

Bolted to the outer-shell is an Actuonix L12 Linear Servo (Model ID: L12-100-210-6-R). The tip of the servo is bolted to the cap of the inner tube, so that when the servo extends, the inner tube will be partially extracted from the outer-shell, exposing the collection rods to the atmosphere. This servo has a 100mm maximum stroke (only 70mm of which is actually used). The high gear ratio of 210:1 provides roughly 14lbs of force behind the actuator at the cost of speed. This gear ratio also ensures that, once the servo retracts, the servo will not be extended by external forces.

Negative Control

The negative control for this experiment is an identical tubing system but lacking a linear actuator. The tubes will be locked in place and will follow the same handling/sterilization procedures as the active tubes.


Both the inner tube and outer tube will be sterilized using 70% Ethyl Alcohol followed by 70% Isopropyl Alcohol. These are commercially available yet powerful antiseptics, neither of which will compromise the integrity of the PVC shell (Source1) (Source2).

With more resources available, further sterilization can (and should) be used to minimize risk of contamination. The techniques used by the LSU LAMB team are as follows:

Sampling rods should be exposed to germicidal ultraviolet radiation (UV-C; 254nm) for 20min, soaked in concentrated sodium hypochlorite for 20min, rinsed with 70% ethanol, and allowed to dry. After 24–48 h, the rods were exposed to ethylene oxide (450–650 mg L− 1) for 4 h at 55 °C and a relative humidity of 30–50%.

The rods should be coated in silicone grease (for bacterial capture).


The microcontroller system uses a ModernDevice RBBB (Really Bare Bones Board) programmed using the Arduino IDE. Previous versions of the microcontroller system used the Arduino Diecimila and UNO boards. The RBBB uses 5V delivered from a battery pack (5x AA Lithiumbatteries). Connected to the RBBB is 1) BLOX MAX 6 series GPS 2) L12 Linear Servo. GPS information dictates when the linear actuator will extend.


The RBBB was programmed using Arduino’s IDE. The .ino uses both the TinyGPS++ and Arduino Servo libraries. The TinyGPS library is very effective at parsing NMEA GPS data streams. The TinyGPS code used to parse the NMEA strings is largely based off of code written by Mikal Hart, but has been edited to accommodate the additional tasks required of the module. You can view this code on GitHub: https://github.com/tristcar/HENRY-1/blob/master/GPS_SERVO.ino. NOTE: This code uses an altitude range of 100 to 130m ASL for testing purposes. Modify these parameters before use.

GPS noise leads to an altitude variation of +/- 5m under good conditions (good satellite lock, no obstructions) but in poor conditions this can range up to +/-20m.

NOTE: This code uses software serial. Be sure to reconfigure the rx/tx pins if you are adapting this project.

if ((gps.altitude.meters() < 110) and servoextended == true and locked == false) {// Tests whether GPS altitude is below extraction range AND that the servo has already extended.
 myservo.write(45); // set servo to start point
 servoextended = false;
 locked = true; // sets the locked variable so that a faulty reading cannot cause the servo to extend again

The locked variable being set to TRUE ensures that faulty GPS readings (or GPS noise) does not cause the servo to extend outside of the desired altitude.

if (locked == true) {

Retracts the servo to its closed position, print statement for serial monitor. After recovery of the module, the RBBB will be connected to the Arduino IDE via USB so that the serial monitor will be viewed. According to the above statement, if the servo has gone through the process of opening, closing, and locking, we should expect to see “Breaking” printed in the serial monitor. “Breaking” would indicate a successful opening of the capsule. This issue can be circumvented by printing all serial monitor data to an SD card as a .csv file.

Microbial Analysis

Assuming successful recovery of the collection module, no signs of contamination, and no mechanical failures, a microbial analysis of the collecting rods can be conducted. Both the negative control and active rods will be transferred to liquid media R2A (amended with 100 μg mL− 1 cycloheximide to inhibit fungi growth). Ideally, rods will be placed in the medium immediately upon recovery. At minimum, transfer should take place no more than 24 hours after recovery. Incubation will be at 4 ̊C for 60 days. Aliquots will be plated onto solid media (R2A) and monitored for colony growth at 20 ̊C. NOTE: This microbial analysis is drawn from and almost identical to the methods used by the LSU LAMB team.

Growth from the negative control rods would indicate in-flight contamination.


73 Tristan Caro KM6GRC


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