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
 * Select three transmission antennas to consider
 * Must be (1) linearly polarized and (2) low gain (omni-directional)
 * Select three receiver antennas to consider
 * Must be directional
 * Provide end to end test of communications system
 * Develop two independent methods of measuring wind speeds

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
 * 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 element
 * Dipole for 144MHz
 * 0.33m
 * Monopole for 437 MHz
 * 0.5m
 * Modified length to accommodate transmit frequency of CANSAT

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

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

Meeting Minutes
MeetingMinutes.pdf