Gateway to Space ASEN/ASTR 2500 Fall 2010
Colorado Space Grant Consortium
Gateway to Space
Fall 2010
Design Document
Team µ-
Written by:
Henry Shennan, Jennifer Nill, Graham Risch, Chelsea Donaldson,
and Jonathan Lumpkin
1 November 2010
Revision C
Revision Log
A/B / Conceptual and Preliminary Design Review / 10.5.2010
C / Critical Design Review / 11.2.2010
D / Analysis and Final Report / 12.4.2010
Table of Contents
1.0 Mission Overview 4
2.0 Requirements Flow Down 4
3.0 Design 4
4.0 Management 4
5.0 Budget 4
6.0 Test Plan and Results 5
7.0 Expected Results 5
8.0 Launch and Recovery 5
9.0 Results and Analysis 5
10.0 Ready for Flight 5
11.0 Conclusions and Lessons Learned 6
12.0 Message to Next semester 6
Page 2 of 15 August 23, 2010
Rev A
Gateway to Space ASEN/ASTR 2500 Fall 2010
1.0 Mission Overview
Team Muon will examine the “dayglow effect” produced when molecular oxygen in the upper atmosphere is excited by fluorescent and resonant processes by observing that molecule’s spectral line emission at 557.7nm. After initial experiments with muon detection using a single photomultiplier tube it was determined that, as a result of dark current processes within the apparatus, the signal to noise ratio of a scintillator plate and photomultiplier tube was far too small, to produce reliable data given the constraints posed by an airborne platform. Thus, it was decided to repurpose the equipment already obtained for that experiment to look at other low-intensity light sources in the upper atmosphere.
We will compare the data we obtain with measurements of oxygen concentration from another group in order to analyze how and if the intensity of the dayglow effect observed correlates with gaseous oxygen concentration, and how that correlation varies with altitude and atmospheric pressure.
A delicate balance must be reached in the discrimination filters leading to the sensor; the photomultiplier tube must not be oversaturated with light, but must be supplied with enough light to allow for accurate detection with a reasonable time of integration. Furthermore, if the beam of the detector crosses the sun, the detector will need to be adequately shielded to prevent a catastrophic oversaturation of the photomultiplier. The two filters necessary to accomplish these goals are a neutral density filter and a spectral line filter. The neutral density filter will ensure that the photomultiplier tube is never overexposed by limiting the maximum radiative flux we are likely to observe to a level safe for the detector. The line filter will discriminate incoming radiation to a 10nm bandpass centered at 557.7nm in order to limit our observations to the dayglow effect produced by oxygen in the mid to upper atmosphere.
Although the photomultiplier tube can operate at extremely low temperatures, the HOBO, the camera and the batteries used for power cannot. Consequently, we must perform a cold test to ensure our satellite is properly insulated. Furthermore, specific tests must be conducted in order to calibrate the scientific instruments on board, including an ambient light test to confirm the isolation of the photomultiplier tube from errant signal sources and a known source test to characterize the noise level and sensitivity of the system.
2.0 Requirements Flow Down
Level / # / Detail / FromBasic Requirements
O / 1 / The Satellite will be launched to a height of 30km and be recovered after landing on November 6 / MS
O / 2 / The BalloonSat will have a maximum mass of 850 grams. / MS
O / 3 / The budget is $300.00 / MS
O / 4 / The balloonsat will take internal and external temperature readings / MS
O / 5 / The balloonsat will carry a camera that will take pictures every 20 seconds. / MS
O / 6 / The internal temperature will not dip below -10 degrees Celsius / MS
O / 7 / The satellite will carry a photomultiplier tube and filters to measure oxygen light emissions / MS
Level 1
System Requirements
S / 1 / The balloonsat will be attached to a weather balloon and have a hole through which the flight string will pass. / O1
S / 2 / The balloonsat must be insulated and heated sufficiently enough to ensure the functionality of the payload. / O4/O6
S / 3 / The balloonsat must be structurally sound and withstand physical stresses during flight to protect the payload. / O1
S / 4 / The balloonsat will not leak light so that only a certain wavelength is measured / O7
S / 5 / A HOBO data logger will record internal and external temperature of the balloonsat / O4
S / 6 / A mass budget and a monetary budget shall be created. / O2,O3
S / 7 / A Canon A570IS Digital camera will be flown. / O5
S / 8 / The balloonsat will carry enough power to operate for a specified period of time during the flight. / O1
S / 9 / The balloon sat will carry all necessary experimental equipment / O7
Level 2
Subsystem Requirements
SS / 1 / The balloonsat will be constructed of foam core and aluminum tape / S3
SS / 2 / Payload must be secured so damage does not occur during flight/landing / S3
SS / 3 / The photomultiplier tube will be filtered by an spectral line filter in addition to a neutral density film to prevent oversaturation and erroneous readings / S9
SS / 4 / A heating circuit shall be implemented, powered by three 9V batteries. / S2
SS / 5 / The balloonsat will be insulated with insulation foam / S2
SS / 6 / A magnifying circuit will be used to amplify power for the PMT / S8
SS / 9 / An Arduino will be flown to collect and store data from PMT / S9
3.0 Design
3.1 Design Overview
The design of our craft consists of a dual-chamber cubic box, where one chamber is insulated and heated to allow the electronics contained within (the photomultiplier electronics, the microcontroller, the camera, and the HOBO logger) to function properly, while the other is open to the outside environment, a single circular aperture on one of the sides to accommodate the filter housing leading to the photomultiplier tube.
3.2.1 Satellite Structure
The craft itself will consist of a cubic solid with dimensions 15cm to a side assembled out of 5mm foam-core board as shown in figure 3.3. A rectangular section along the craft’s bottom surface of dimensions 15cm by 5cm by 5cm will be un-insulated and open to the outside air, whereas the remaining larger section will be insulated with 7mm plastic foam and will contain all of the craft’s electronics. The two sections will be separated by an insulated foam-core divider and bridged by the 8 power and data wires to the photomultiplier tube. The insulated section of the spacecraft will be heated with a resistive heating element consisting of 3 9V batteries and 4 4Ω ceramic resistors in series in order to keep the internal temperature above --10°C. The craft will be assembled following the procedure described in the Gateway to Space lecture of 9 September 2010, whereby a 90° groove is cut into the foam-core and hot glue is used to cement the interior of the joint while aluminium tape reinforces the outer edge. This method of construction has several advantages in that it is durable, relatively simple, and low-weight when compared to alternatives such as aluminium. Finally, a central bushing will be run through the center of the craft to accommodate a 2.4mm braided Dacron tether line. The line will be fastened to the craft by two figure-8 knots in the line that butt up against non-abrasive bushings at either end of the center tube.
3.2.2 Detector Subsystem
The detector subsystem will consist of a photomultiplier tube (Hamamatsu H6534SEL) preassembled in a light-tight housing with a DC/DC converter (which allows a 12V power supply to power the 1000V tube). A dedicated 6Ah battery will power the tube for the duration of the experiment. Two 25.3mm diameter filters, the neutral density filter and the spectral line filter described in the introduction (and characterized below) will be assembled back to back in the light-tight tube that leads to the aperture of the photomultiplier (figure 3.1). The spectral line filter has a 10nm half-power bandpass centered at 560nm with 3dB points at 554nm and 464nm. Light entering the apparatus will first be filtered and attenuated by the two optical elements, and then detected and amplified by the photomultiplier tube, which will induce a current in the output loop that can be measured and recorded by the Arduino microcontroller.
Figure 3.1: Photomultiplier Assembly
Figure 3.2: Line Filter Spectral Response Curve, λ0=560nm
(Image from Newport Optics Corp.)
3.2.3 Secondary Data Collection Devices
In order to fulfill its secondary mission objectives, the craft will also include a Canon A570IS digital camera which will take photographs out of a portal in the side of the spacecraft in 15 second intervals. The camera will have its own onboard power source of two AA lithium batteries and its own onboard memory to store captured photographs. The camera will be activated prior to launch by a switch on one of the exterior sides of the spacecraft. The remainder of the secondary mission objectives will be accomplished using a HOBO data logger. The HOBO will be located within the insulated, heated portion of the craft, and will record the internal temperature and humidity of that portion of the craft. The extendable second temperature probe of the HOBO will be routed to the uninsulated second section of the craft, and will record the ambient temperature adjacent to the cosmic ray detector. The HOBO will be activated prior to launch, and will remain active until the craft is recovered.
3.3.1 Functional Block Diagrams
Figure 3.4: Functional Block Diagram of the Flight Component
3.3.2 Design Drawings
Figure 3.5: Flight Component Design
3.5 Discussion of Requirements Met
The aerial component of our mission has been designed to ascend to the specified altitude of 30-40km and return safely without endangering any of the other payloads. The spacecraft will carry enough batteries to power instruments for the entire 90m duration of the flight. The total mass of the craft with payload is projected to be 938g (with a mass allowance of 10g, for details please see section 5), which does not yet satisfy the 850g limit set by the requirements in the RFP, although we are working to remedy this problem. Our design includes the HOBO, Canon camera, internal heater, and temperature sensors mandated by the requirements, and satisfies the requirement that the craft be constructed of foam-core board. Our budget does include a $25.00 lump sum for spare parts and other unanticipated expenses and still meets the requirement that the total budget be under $300 (for details, please see section 5). The craft is designed to be reusable, and will include identification and an American flag on an exterior surface. Finally, onboard heaters will ensure that the internal temperature of the craft remains above -10C and a central PVC tube with rubber bushings will ensure that the tether is not damaged during the mission.
4.0 Management
The team responsible for the completion of this project will be organized in such a way as to ensure that no one individual is wholly responsible for any given subsystem. This organizational structure makes it much less likely that any subsystem will fail to be completed, and also provides a means by which mistakes can be caught easily and early while reinforcing team structure. Due to his prior experience with cosmic ray detectors in particular, and photomultiplier tubes in general, Henry will be leading the design, construction, and testing of the mission payload. The construction of the satellite structure (box, wiring, etc.) will be led by Jon with the assistance of the rest of the team throughout the build. Testing was led by Chelsea and Graham and every other team member assisted with separate tests in order that at least 3 people were present for every individual test. Programming will be done by Jen and Henry with a team overview to confirm that it performs to the level necessary for mission success.
The design documents are assigned by section to each person with at least one other person reviewing the writer’s work to ensure cohesiveness and thoroughness. Chelsea is responsible for the presentations with the assistance of the rest of the team. All other vital tasks have been spread between members with a reviewer and/or partner for each task to maintain efficiency while ensuring that all tasks are completed correctly and on-time by preventing any subsystem from relying entirely on the input from any single team member.
Figure 4.1: Team Structure
Figure 4.2: Project Schedule
28/10/2010 / Structural Testing (Whip, Drop Test- again)29/10/2010 / PMT Calibration
30/10/2010 / HOBO Testing and Data Collection
30/10/2010 / Arduino Programming
30/10/2010 / Cold Test & HOBO Test (during cold test)
31/10/2010 / Arduino Maintenance
11/01/2010 / Light Leak Test
11/02/2010 / Launch Readiness Review Presentations
11/02/2010 / DD revision C due 07:00
11/04/2010 / Mission Life Test
11/05/2010 / Weigh-in and aerial component turn-in
11/06/2010 / Data Collection
11/08/2010 / Begin data analysis
11/07/2010 / Team Meeting 9
11/14/2010 / Team Meeting 10
11/30/2010 / Final team presentation to the class
12/04/2010 / ITLL design expo 09:00-16:00
12/04/2010 / DD revision D due
12/21/2010 / World Ends
Figure 4.3: Team Member Information
Name / Contact InformationHenry Shennan / 303-564-7575
Jennifer Nill / 303-241-7143
Jonathan Lumpkin / 970-669-8776
Chelsea Donaldson / 970-331-6409
Graham Risch / 678-463-1374
Graham
5.0 Budget
The management of the team’s budget will be split between Henry Shennan and Graham Risch. Shennan will be responsible for the budgets as they concern the main mission: the cosmic ray detector. Risch will be responsible for the budgets as they apply to the remainder of the mission, and will have supervisory capacity over Shennan for this and matters concerning the budget. Both Risch and Shennan will meet a minimum of 3 times over the course of the project to make sure that both the weight and the cost of the project fall within the bounds specified in the mission requirements.