Small Satellite Technology

JPL Small Satellite Weather Balloon Technology Design Project

Project Goal
To demonstrate a proof of concept for a radio science technique to measure the dynamics of a planetary atmosphere using a capsule in flight. [pantheondesignproject.wordpress.com]

Project Background
An important measurement in the study of planetary atmospheres is the profile of wind speeds from the upper atmosphere to the surface. Entry and descent probe measurements of the winds of Venus, Jupiter, and Saturn’s largest moon Titan have been made by Doppler tracking of Pioneer and Venera probes, the Galileo probe, and the Huygens probe, respectively. The winds in the upper atmosphere of Venus were also measured by tracking the Soviet VEGA balloons. The most significant shortcoming to these measurements is that they provide one profile of winds at a single location. The dynamics of planetary atmospheres can be better characterized if the winds are measured simultaneously at multiple locations. One concept for doing this is to have a single ground station such as a planetary lander that would release multiple balloon-borne transceivers that continuously transmit to the ground station. By making precise frequency measurements at the ground station of the signal from each balloon capsule in flight, the Doppler shift of the signal can be used to provide an accurate measurement of the balloon dynamics and from this the wind dynamics can be inferred.

Project Goals
Electrical Requirements


 * Design, build, test communications system for measuring frequency at sampling rate TBD
 * 433 MHz
 * Use a tape measure for a transmitting antenna
 * Select three receiver antennas to consider
 * Must be directional
 * Provide end to end test of communications system

Mechanical Requirements


 * Mass (FAA)
 * Less than 2.72 kg
 * Dimensions (CubeSat standard as defined by Cal Poly)
 * Cube 10 x 10 x 10 cm, known as 1U
 * Temperature (VAST data collection)
 * Internal requirements
 * No less than 0 °C and no greater than 40 °C
 * Goal: 0°C - 10°C
 * External minimum reaches -50 °C

Cube Material

 * Initial Cube Material Research


 * Final Cube Material:

From the initial design review of material we chose DOW "Utilityfit" Insulation, but after researching the DOW website, we found DOW TUFF-R insulation to be the best option for the mass design parameters specified below:


 * Federal Aviation Administration mass requirement
 * Entire system - structural and communications/electrical - can be no more than 2.72 kg
 * Current mass
 * Total: 0.5 kg
 * Includes: carbon fiber walls, aluminium blocks, insulation

Heat Transfer
The Heat Transfer Goals are to finalize an insulation thickness for the cube that will keep the electronics at their operating temperature in a worse case scenario.

Preliminary EES Solution


 * Required Specifications:
 * Minimum Inside Cube Temperature of -15°F
 * Altitude Dependent Values
 * Assumptions:
 * Carbon Fiber Structure Negligible
 * DOW Utilityfit Insulation
 * Generated Heat is removed by convection to the surroundings and radiation by the box
 * Altitude of 80,000ft
 * Solution:
 * Insulation Thickness
 * Total Power Loss

Finalized EES Solution
 * The finalized solution adds radiative heat transfer as well as validates the prior exclusion of carbon fiber convective heat transfer in the code.


 * Required Specifications:
 * Minimum internal temperature at 0 °C
 * Must maintain operational temperature TBD of transmitter hardware
 * VAST data suggests minimum external temperature of -50 °C
 * Assumptions:
 * DOW TUFF-R Insulation
 * Generated Heat is removed by convection to the surroundings and radiation by the box
 * Altitude of 80,000ft
 * Solution:
 * Insulation Thickness
 * Total Power Loss
 * Carbon Fiber Wall Convective Heat Transfer 0.056% difference
 * Negligible due to wall thickness

Electrical Engineering
Electrical device selection is based on a worst case scenario model. The component requirements are as follows:


 * Transmitter Requirements:
 * 420-450 MHz
 * Transmit minimum of 53 miles Line of Sight (LOS)
 * For 80,000 feet altitude and 60 mile horizontal distance


 * Board Requirements:
 * Type of oscillator
 * Silicon or Crystal
 * High clock speed

Flight Elements
Initial Flight Elements:

Transmitter Options:

Board Options:

Crystal Oscillator Selection:

Specifications:
 * SG-8002JF-PCC (Digikey)
 * 1 MHz-125 MHz
 * Can be used with Spartan 3E TQ144 and CP132
 * 3.3 V (max)
 * 28 mA (max)
 * -20C ~ +70C
 * 7.1mm X 4.6mm X 1.5mm

Interim Flight Elements

Other internal flight elements were added to allow for proof of concept design to progress to a future cubesat design.


 * CANSAT Kit Rev 2
 * Pressure sensor
 * Temperature sensor (not included)
 * TMP37 Analog Devices
 * One additional peripheral port - use of which is TBD
 * Transmitter
 * Meets AX.25 protocol
 * Transmits at 433.92 MHz
 * 5 g
 * Power
 * 9 V provides 5 hours of operation
 * Up to 5 V transmit power
 * Arduino compatible microcontroller

Ground Element

 * Yagi antenna
 * CANSAT Receiver
 * Directional

Antennas

 * Flight Antenna (Transmitting)
 * 433 MHz quarter-wave dipole
 * 17.3 cm length

Wind Measurements

 * GPS
 * VAST system
 * Doppler shift
 * Use communications system to accurately measure doppler shift
 * Use doppler shift to calculate satellite LOS speed
 * Third method: external sensor
 * Currently researching

Cube Design

 * SolidWorks Cube Model:


 * Following CubeSat standard
 * 10 x 10 x 10 cm, known as 1U
 * Carbon Fiber Panels with Pumpkin CubeSat inspired cutouts
 * Cutouts to adhere to hardware requirements
 * Threaded Aluminum blocks for cube panel connections
 * Milled Insulation to hold desired electronic operating temperature


 * Current Cube Structure Prototype:

A rapid prototyping machine was used to construct the initial prototype and basal wood cubes stood in place of the aluminum blocks. The insulation was not included.


 * Structure uses six 0.96 x 0.96 cm carbon fiber squares
 * 4 mm difference accounts for two 2 mm thick carbon fiber panels
 * May need to account for screw heads by countersinking or further reducing panel dimensions

Manufacturing

 * Tooling Plate:

The Tooling Plate is used for cutting out the carbon fiber panels. The tooling plate is mounted in our Haas CNC mill, the mill is zeroed to the tooling plate using reamed hole in top left corner. Carbon fiber blanks are mounted to the tooling plate and cut out using the mill.


 * Cube Corners:

The Cube Corners are threaded to join all eight corners of the cube, made using SHARP manual mill.

Electrical Engineering
Link Budget Assumptions

Link Budget Results


 * Free space loss: -112.17 dB
 * EIRP:
 * Best: 27.99 dBm
 * Worst: 26.99 dBm
 * Receiving antenna effective aperture:
 * Best: 0.1911 m^2
 * Worst: 0.07611 m^2
 * Received power:
 * Best: -77.18 dBm/-107.18 dBw
 * Worst: -88.18 dBm/-118.18 dBw

Selected Transceiver

BHX2-433-5-SMA
 * Radiometrix product
 * Frequency: 433 MHz
 * Transmit power: 500 mW
 * Receiver sensitivity: -118 dBm

Antennas

Transmitting antenna Ground station/Receiving antenna
 * 17.3 cm quarter-wave dipole antenna
 * 430 MHz yagi antenna

Cold Chamber Test
Purpose: To obtain a relative range for the temperature drop inside & outside of the cube, for verification that the insulation system can maintain an electrical operating temperature between 0°C and 10°C.

Results: Graph the Temperature Drops vs. Time


 * Outside of cube to Inside of cube
 * Inside of cube @ start and end of test
 * Chamber @ start and end of test

Cold Chamber Tests

Results


 * Temperature Validation Test:


 * Completed Feb. 13th & Feb. 14th

Cold Chamber Decreasing Temperature Range
 * 15°C to -58°C
 * Minimum Temperature reached within 1hr

Cube Design Analysis Steady State Heat Transfer Code Insulation Top Closure
 * Includes Heat generation
 * 9 Volt Batteries
 * Handwarmers
 * Air tight

Drop Test
Purpose: To verify that the external structure can withstand landing impact stresses and analyze design problems from fracture points.
 * 1.5m Drop
 * Kibbie Dome Parachute Drop

Results: Visual Assessment (VAST) Graph - Accelerometer Data of Impact (Tensegrity Group)

Antenna Chamber Test
Antenna chamber at Gonzaga University, 3 meters in length, will be used to conduct the tests on both transceivers. Will perform the radiation pattern, transmit power, receiver sensitivity, and EIRP test at room temperature then again with the transceivers cooled to 10°C.
 * 3D radiation pattern
 * Verify link budget
 * Transmit power
 * Receiver sensitivity
 * EIRP

Project Risks

 * Thermal overheating or freezing of electronics
 * Limited cold chamber testing time
 * Further reducing structure size to compensate for screw heads and wall thickness to meet CubeSat standard limits internal space for communications system
 * Cube fabrication may delay drop testing
 * Spring launch dependent on weather
 * Time to acquire components - shipping, back order
 * System power
 * Transmission distance

Project Timeline
November December January February March April May
 * Finalize communications hardware
 * Order most components
 * Verify communication link
 * Finalize structure
 * December 6 Snapshot 2
 * December 20 complete prototype
 * January 23 Begin structure testing
 * February 10 Complete all testing
 * Start compiling paper
 * Mid-March 2014 flight date
 * Evaluate for areas of improvement
 * April 25 Finalize paper
 * May 2, 2014 Engineering Expo

Presentations
Old_Design_Review_Presentation.pdf

Progress....pdf

Progress__October_17.pdf

Snapshot 1.pdf

Snapshot 2.pdf

Design Review.pdf

Meeting Minutes
Meeting_Minutes.pdf