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<span class="style6">ESMD Course Material : Fundamentals of Lunar and
Systems Engineering for Senior Project Teams, with Application to a
Lunar Excavator</span><br />
<br />
Contact: David Beale, dbeale@eng.auburn.edu</div>
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<div>
<h1><a name="Chapter3SystemsEngineeringExampleofaCubeSatellite">Chapter
3 Systems Engineering Example of a Cube Satellite</a></h1>
<p class="style11"><strong>by David Beale and Joseph Bonometti</strong></p>
<w:sdt sdtdocpart="t" docparttype="Table of Contents" docpartunique="t" id="209345378">
<p>
Contents<w:sdtpr></w:sdtpr></p>
<ol>
<li>
<a href="#Chapter3SystemsEngineeringExampleofaCubeSatellite">Chapter 3 Systems Engineering Example of a Cube Satellite</a><o:p></o:p><ol>
<li><a href="#ProjectOverview">Project
Overview</a><o:p></o:p></li>
<li><a href="#ConceptStudies">Concept
Studies (NASA Pre-Phase A)</a><o:p></o:p></li>
<li><a href="#ConceptandTechnologyDevelopment">Concept
and Technology Development (NASA Phase A)</a><o:p></o:p></li>
<li><a href="#PreliminaryDesignandTechnologyCompletion">Preliminary
Design and Technology Completion (NASA Phase B)</a><o:p></o:p></li>
<li><a href="#FinalDesignandFabrication">Final
Design and Fabrication (NASA Phase C)</a><o:p></o:p></li>
<li><a href="#SystemAssemblyIntegrationTestandLaunch">System
Assembly, Integration, Test and Launch (NASA Phase D)</a><o:p></o:p></li>
</ol>
</li>
</ol>
</w:sdt>
<p>
The Systems Engineering (SE) method explained in Chapter 2 is
demonstrated by the design of a cubic
satellite ("cubesat") named the AS-1, as was performed by a student
team. The cubesat is a complex multidisciplinary project with each
subsystem being designed by a team of a particular discipline suited
to that subsystem. This
example is intended to present an example of the steps in the SE process, with
comments presented in italics. The
full report (AUSSP, 2007) describes
the design of cubesat AS-1, and can be found at <a href="http://space.auburn.edu/page_attachments/0000/0046/Spring_2008.pdf">http://space.auburn.edu/page_attachments/0000/0046/Spring_2008.pdf</a> (although
the document is periodically being updated as the project
progresses). Pre-Phase A and Phase A were
completed, and the project is well on its way through Phase B with a
baseline design and some detailed designs
documentation. The
eleven SE functions are applied in each phase, that includes the five around the
triangle and the other six SE functions. Excerpts
of the report were used to create this streamlined example. SE tools
(e.g. block diagrams; mass, power, cost and link budgeting; trade
studies; and failure mode analysis) were applied to SE functions
when warranted. The
report is periodically updated as the team progresses toward an
operable system. </p>
<p>
<img alt="AubieSat1" border="0" height="534" src="SiteImageFiles/Chapter3/image003.jpg" v:shapes="Picture_x0020_1" width="576" /></p>
<p>
2‑1 Cubesat
Structure, aluminum housing with solar panels (grey)</p>
<h2>
<a name="ProjectOverview">Project
Overview</a><o:p></o:p></h2>
<p>
The CubeSat Project began as a collaborative effort between
California Polytechnic State University San Luis Obispo and <st1:place w:st="on"><st1:placename w:st="on">Stanford</st1:placename> <st1:placetype w:st="on">University</st1:placetype></st1:place>’s
Space Systems Development Laboratory. The
effort led to standards for the design of 10 cm cube, 1 kg
"picosatellites" that can be built by student teams at universities
throughout the world. The
program, design specifications and test requirements are described
at <a href="http://cubesat.org/">http://cubesat.org/</a>.
Cubesat projects are small-scale, low-cost, multidisciplinary
projects where student teams can learn about and apply Systems
Engineering.</p>
<p>
The mission
objective for this student team is to test a GaN-based Ultraviolet
(UV) photodetector
in space. The
student team was tasked to design, build and operate a CubeSat in
Low Earth Orbit (LEO) carrying the photodetector as the payload. The
cube structure is an enclosed aluminum box with solar cells clamped
on the outside walls. Antennas
are deployed perpendicular to the faces at the corners. Internals
include sensors, a camera and printed circuit boards. </p>
<p>
The launch is currently planned to be
onboard a Russian
Dnepr rocket from <st1:place w:st="on"><st1:country-region w:st="on">Kazakhstan</st1:country-region></st1:place> in
Fall 2010.
Once in low earth orbit, the satellite will be deployed
using the standard Poly Picosatellite Orbital
Deployer (P-POD). The
orbit is 700
km altitude, sun-synchronous,
near-polar, 98° inclination orbit, Orbital
Period: +/- 98 minutes, with 3-5 and 10-14 minute communications windows/day. The
satellite is 1
kg, 100x100x113.5mm,
with low
power and low data rate. The
cube is powered by solar cells.<o:p></o:p></p>
<p>
The team has made a report (AUSSP,
2007). The
satellite system is not finished, the project is currently in Phase
B: Preliminary Design and Technology Completion.</p>
<p>
Hierarchy of management and division of responsibilities was first
established and duties assigned. The <b>program
manager </b>is, in this
case, the faculty advisor. The <b>project
manager</b> is
responsible for scheduling the development cycle, defining mission
requirements and goals, as well as the overall success of the
project. He
is also responsible for keeping the project costs within budget. The <b>systems
engineer</b> is
responsible for guiding the engineering of the project; for
defining, verifying and validating system requirements’ flow down to
each subsystem; and for the integration and test phases of the
project. He/she is also responsible for coordinating system trade
studies, managing critical resources/interfaces for each subsystem
and failure mode and risk analysis. Each <b>subsystem
lead</b> is responsible
for the development and testing of their individual subsystem, and
must remain aware of how changes in their subsystem affect other
subsystems and the system as a whole. The
subsystem leads were selected in anticipation of the probable
subsystems, i.e. payload, C&DH (Command and Data Handling), COMM
(Communications), EPS (Electrical Power System), ADC (Attitude
Determination and Control), Structures and Mechanisms, Thermal and
Ground Station.</p>
<p>
</p>
<p>
<img border="0" height="225" src="SiteImageFiles/Chapter3/image015.gif" v:shapes="Picture_x0020_2" width="576" /></p>
<p>
2‑2 Management structure. The bottom most level are the
subsystem team leads and team members of that subsystem.</p>
<h3>
Systems Engineering Team and Subsystems Teams Responsibilities<o:p></o:p></h3>
<p>
<a name="teams"></a><b>Systems Engineering Team – </b>Works for the
systems engineer and may be a team of subsystem leads.
Responsible for the 11 systems engineering functions. Analyzes
the characteristics of the mission such as orbit and environment.
Ensure all subsystems interface properly and work as one fully
integrated satellite. Guide the systems engineering of the
satellite, ensuring that all mission requirements are met, while
bridging the various engineering disciplines. They manages mass and
volume budget and oversees all other budgets except cost. They
maintain a timeline of events (ConOps), mission profile and anomaly
(abort, reboot, reduced operations, end of life, etc.) procedures. </p>
<p>
<b>Ground Station Team </b>–
Designs, builds, and operates ground station antennas, mounting,
enclosure, and computer. Selects and installs operating programs and
data processing. Handles communication with AS-1 and tracking of
other amateur satellites.</p>
<p>
<b>Communications Team </b>–
Designs, builds, tests the onboard communication system including antennas, transceivers and TNCs. Manages
the link budget.</p>
<p>
<b>Attitude Determination and Control Team– </b>Designs,
builds and tests the ADC subsystem to achieve solar cell orientation
to the sun for the EPS, and antenna orientation for communication.
The subsystem includes magnets, hysteresis dampeners, and an
attitude determination algorithm for a desired solar cell orientation.</p>
<p>
<b>Command and Data Handling Team </b>–
Designs the command and data architecture. Selects hardware
components, designs circuit board layout and programs the processor.
Selects sensors and incorporates them into the design. Manages the
data budget.</p>
<p>
<b>Electrical Power System Team </b>–
Designs, builds and tests the power subsystem, including solar
cells, rechargeable batteries and power regulators. Manages the
power budget.</p>
<p>
<b>Structures Team </b>-
Designs and builds the structure of the satellite, including the
mountings for all components, fulfilling compliance with CubeSat
specs and system requirements, including launch vibration. Oversees
the vibration and load testing.</p>
<p>
<b>Thermal Team </b>–
Conducts the steady-state and transient thermal analysis of both the
internal and external structure to ensure component thermal
requirements are met. Oversees the thermal vacuum testing and
maintains the thermal budget and temperature range for all
subsystems.</p>
<p>
<b>Payload Team </b>–
Develops hardware components needed to accompany payload and ensures
the design meets requirements set by the scientists. Oversees
the payload functions testing.</p>
<p>
After recruitment operations are completed, the new student team -
with guidance from the program manager and the project manager -
works as a group to refine the goals, setting milestones with
deliverables. Next, the team defines the
requirements of the system and the subsystems. Subsystem leads,
students who are designated by management to oversee each subsystem,
play an important role in this process. Because Subsystem Leaders
have usually been involved in the project for multiple semesters,
they serve as a resource for new students and are able to share what
works and what doesn’t from their experience. During the next series
of exercises, the team develops a <i>work
breakdown structure (WBS)</i> which
is a list of activities that must be performed to reach their
subsystem goals by the end of the semester. This clarifies in the
students’ minds what work is done by each subsystem team. At this
juncture, they are ready to choose which subsystem team to join. A <i>responsibility
matrix</i> is established
for each student and is signed by the student, the project manager
and the program manager. All subsystems then work together to create
a <i>network diagram
schedule</i>. Finally a <i>Gantt
chart </i>project schedule, is made
and used as a guide and a tool for assessing progress and for
assigning deadlines throughout the semester.</p>
<p>
The process of incorporating project management continues once the
technical work has begun. During a short session at the beginning of
each meeting, subsystem members are asked to communicate to the
entire group what work has been done, what problems are being
encountered, and what effect their status will have on the overall
project schedule. These sessions allow a forum for problem solving
as well as a reinforcement to students that they are accountable to
the team. Additional daily assignments may be made to individual
students by management in an effort to ensure preparedness for work
in the lab. Students will participate in several design reviews
throughout the semester. Reviews require students to create and give
a presentation to the group and invited guests. All students are
required to keep daily documentation of their work on AS-1 and are
required to properly update their subsystem’s portion of the AS-1
Manual to reflect their contributions to the semester’s work. All
student-produced documents and results are overseen by subsystem
leads and management to ensure proper progress is being made.
Leaders then work with students to overcome obstacles and complete
projects.</p>
<p>
The systems engineering process is now demonstrated. The steps of
Chapter 2 are followed in this example, starting with
Pre-Phase A, going onto Phase A and Phase B. In
each Phase some of the 11 SE functions are applied. Figures 2-3 and
2-4 are included to guide the process. The
demonstration is by no means comprehensive. And
often it is difficult to determine whether a particular team's action
should have occurred in one particular phase, or more appropriately
in another. The
ideal approach is to not allow the details of the "process" to
become a burden or the end goal in itself, but rather treat the
process as a useful tool, being somewhat flexible and not rigid, and
forge ahead with the work's true objective: producing the best
functional satellite design. </p>
<p>
KEY:<o:p></o:p></p>
<p>
<span class="style12">Instructions</span> are in regular font
<span class="style14">red</span></p>
<p>
<i><span class="style12">Comments</span> are in unbold italics (except for headings)<o:p></o:p></i></p>
<p>
<img border="0" height="360" src="SiteImageFiles/Chapter3/image021.gif" v:shapes="Picture_x0020_66" width="480" /><o:p></o:p></p>
<p>
2‑3 The System Engineering Functions, including the iterated
functions shown around the triangle</p>
<p>
<img border="0" height="331" src="SiteImageFiles/Chapter3/image022.gif" v:shapes="Picture_x0020_67" width="448" /></p>
<p>
2‑4 The project life-cycle as a Vee chart (R/A/C are the
<span class="style14">R</span>equirements, <span class="style14">A</span>rchitectural Design
and <span class="style14">C</span>onOps steps of Figure 6, SAITL is
<span class="style14">S</span>ystem <span class="style14">A</span>ssembly,
<span class="style14">I</span>ntegration, <span class="style14">T</span>est and
<span class="style14">L</span>aunch)</p>
<h2>
<a name="ConceptStudies">Concept
Studies (NASA Pre-Phase A)</a></h2>
<h4>
<b>Purpose: </b>The
purpose of Pre-Phase A is to produce a broad spectrum of ideas and
alternatives (i.e. concepts) for the mission. The
focus is on the mission, specifically mission architecture, mission
requirements, and mission operation. <o:p></o:p></h4>
<p>
<b><i>Systems Engineer's Tasks:</i></b> Leads
all Pre-phase A activities with support from subsystems lead
personnel. Begin
documentation process.<o:p></o:p></p>
<h3>
<strong>11 Systems Engineering Functions</strong></h3>
<p>
<i>Input</i></p>
<p>
The mission needs, which come as a mission statement and/or mission
objectives, come from the project sponsor. The
team should make sure the sponsor’s needs are understood as well as
those of all other stakeholders. </p>
<p><st1:place w:st="on">
Mission</st1:place> Objective: Determine
if a small satellite platform and GaN-based Ultraviolet
photodetector sensor can be designed, built and operated by a team
of university students<o:p></o:p></p>
<p>
<i>Comment: In
this case the mission objective came from NASA and a professor, as a
challenge to the students. The
team believed that they could build a satellite, however they
wondered how they could get it into orbit on a small university
budget. Here
is where they tried to do their first trade study; they considered
other methods of launching, but none were found. An
investigation led them to the cubesat program and cubesat
requirements. The
GaN-based Ultraviolet photodetector is considered the payload. <o:p></o:p></i></p>
<p>
<i>Architecture and Design Development<o:p><a name="Chap3_PrePhaseA_A&D_Example"></a></o:p></i></p>
<p class="style14">
Visualize highest level systems and interfaces. List
the functions that must be performed. Consider several strawman
architectures. Put
in block diagram form. For
example, the Shuttle Transportation System consisting of option 1)
orbiter, solid boosters and external tank or option 2) orbiter,
solid boosters and two external tanks. </p>
<p>
Architecture and Design: The
mission elements and interfaces will consist of the cubesat
satellite (with scientific payload), ground station and rocket. These
three subsystems are called the tier 1 systems. The
entire system will be called the cube satellite system or cubesat
system (CSS). <o:p></o:p></p>
<p>
Interfaces:<a name="ICD_PrePhaseA"></a> The payload
(GaN sensor) is interfaced to the satellite. The
satellite sends data wirelessly to the ground station. A
deployer (P-Pod) on the rocket will store and then launch the
cubesat. <o:p></o:p></p>
<p><o:p>
</o:p></p>
<p>
<table align="left" cellpadding="0" cellspacing="0">
<tr>
<td height="28" width="94"></td>
</tr>
<tr>
<td></td>
<td>
<img height="99" src="SiteImageFiles/Chapter3/image023.gif" v:shapes="Organization_x0020_Chart_x0020_29" width="282" /></td>
</tr>
</table>
<o:p> </o:p></p>
<p><o:p>
</o:p></p>
<p><o:p>
</o:p></p>
<p><o:p>
</o:p></p>
<p>
2-5. Cubesat system through tier 1 systems.</p>
<p>
<i>In most cases there will be more
than one architecture, but this team was constrained by the CubeSat
requirements. Next
the team considered how it would operate. The
Operations Concept describes how the system will operate.<o:p></o:p></i></p>
<p>
<i>Concept of Operations (ConOps)<o:p><a name="PrePhaseA_ConOps"></a></o:p></i></p>
<p class="style14">
The events which ensue from the moment the system is deployed, shown
on a time scale and/or as sequence of events. The
Operations Concept is initially developed as a draft concept during
Pre-phase A, with refinement throughout the lifecycle, until the
flight operations plan is completed in Phase D. </p>
<p>
Concept of Operations
(ConOps): The cubesat will ascend to orbit on the rocket housed
inside the P-Pod deployer, be deployed into space, signal the ground
station to start mission operations, perform systems check, acquire
sensor data and transmit it back to earth.<o:p></o:p></p>
<p>
<i>Derived Requirements</i> <i>Development </i> </p>
<p class="style14">
The mission statement/objectives are worked to mission requirements. The systems
engineer leads this activity with strong support from subsystem
personnel. Requirements
are often written as “shall” statements. <o:p></o:p></p>
<p class="style9"><st1:place w:st="on"><st1:city w:st="on">
Mission</st1:city></st1:place> (“Level
1”) Requirements<a name="PrephaseA_requirements"></a>:<o:p></o:p></p>
<p class="style8">
The mission shall be in
accordance with the CubeSat Design Specifications. <o:p></o:p></p>
<p class="style8">
The satellite shall be
capable of being launched from a Russian DNEPR rocket going to LEO.<o:p></o:p></p>
<p class="style10">
</p>
<p class="style10">
Validate and Verify<o:p></o:p></p>
<p class="style14">
Check that the architecture, ConOps
and requirements are mutually consistent, and mission statement and
needs are met. Show
that the right system designs have been chosen. Develop
a validation plan to measure performance based on mission
requirements.<o:p></o:p></p>
<p>
Validation Plan: In
Phase D, the cubesat system will be validated by performing a dry
run mission on earth, beginning with a mock deployment from a P-Pod,
and with the ground station as operations center. <o:p></o:p></p>
<p>
<i>Other SE Functions<o:p></o:p></i></p>
<p class="style14">
Begin SEMP, begin assigning
responsibilities. Document
results of the systems engineering functions in a report and present
at MCR (Mission Concept Review). Create
an electronic library. Documents stored in the
electronic library should include: ConOps, Architecture and Design,
Requirements, Resources Budgets, trade studies. <o:p></o:p></p>
<p><st1:place w:st="on">
<em>Mission</em></st1:place><em> Environment:</em><o:p></o:p></p>
<p>
Orbital Analysis<o:p></o:p></p>
<p class="style7">
Analysis was performed using Satellite
Tool Kit (STK) from data available from Celestrack for other
university CubeSats. The typical CubeSat orbit has the following
characteristics:<o:p></o:p></p>
<p class="style8">
Inclination: 98°<o:p></o:p></p>
<p class="style8">
Altitude: 650 – 800 km<o:p></o:p></p>
<p class="style7">
The RAAn is formulated specifically to
give the satellite a nearly constant-sun, sun synchronous orbit. The
orbital plane proceeds through the year to maintain this
constant-sun feature. This orbit is also almost polar, allowing
ground stations at any location on Earth to communicate with the
satellite at some point in time.<o:p></o:p></p>
<p class="style9">
Environmental Analysis<o:p></o:p></p>
<p class="style8">
The Exosphere<o:p></o:p></p>
<p class="style7">
At 650 – 800 km altitude, the exospheric
mass density is between 10<sup>-14</sup> and
10<sup>-15</sup> kg/m<sup>3</sup>. The temperature ranges between
750K and 1000K, but the low density means there is essentially no
heat capacity, and no conductive heat transfer.
Molecular oxygen is
severely depleted at this altitude
because its bonds are easily broken by the incident UV radiation. In
this vacuum, tin-plated parts may 'whisker' causing short circuits.
The suggested mitigation is a conformal coating.<o:p></o:p></p>
<p class="style7">
Plasma<o:p></o:p></p>
<p class="style7">
In plasma, with a negatively-grounded
electrical system such as AS-1, the exposed charged areas, such as
solar cell contacts, can cause plasma arcing. This is usually only
severe in high-voltage arrays, such as the International Space
Station, which has more than 100V on the solar panels. The arcing
may be dissipated by a Zener diode and low-resistance,
high-power dissipation resistor.<o:p></o:p></p>
<p class="style7">
Radiation<o:p></o:p></p>
<p class="style7">
AS-1 orbit will take it through the VanAllen radiation belt's South
Atlantic Anomaly and the outer electron belt at high latitudes.
AS-1's 1.5mm aluminum shielding
will cut out electrons below 1MeV, and protons below 10MeV. The
remaining flux sums to 1 or 2 rads/day. With COTS parts life
expectancy at 2krads, AS-1's electronics should avoid TID damage for
about 10 years. The solar cells, however, have no shielding, and
will experience a dose rate of about 2x10<sup>3</sup> rads(Si)/day. Because
our Improved Triple Junction cells use InP2 and GaAs, they have
increased radiation hardness over Si systems. The manufacturer
specifies that the cells will function at 88% of power after
receiving 5x1014 1MeV/cm<sup>2</sup> flux.
This corresponds to about 107 rads, which should take about 10,000
days, significantly longer than the batteries will last.<o:p></o:p></p>
<p class="style7">
Micrometeoroid/Orbital Debris<o:p></o:p></p>
<p class="style7">
Micrometeoroids are small, naturally
occurring, particles that may impact the spacecraft. The
distribution of their size and energy is statistical, but lower
nearer the atmosphere, where they tend to re-enter. It is assumed
that for a short duration mission, such as AS-1, micrometeoroids
will not be a significant cause of failure, and
that if they were, not much could be done
within our budget to prevent it. Orbital Debris is debris from
man-made sources, such as rocket explosive bolts, or entire
nonfunctional satellites. Orbital Debris tends to be worse in
popular orbits. A detailed analysis has not yet been performed on
the probability of impact micro-meteoroids or orbital debris.<o:p></o:p></p>
<h2>
<a name="ConceptandTechnologyDevelopment">Concept
and Technology Development (NASA Phase A)</a></h2>
<p>
<i>The effort now focuses the attention on the cubesat satellite
itself, since the deployer and rocket exist</i>.</p>
<p>
<b>Purpose: </b><span class="style1"><b>The
purpose of Phase A is to determine the feasibility and desirability
of a system and establish a single approach and baseline system
architecture. (A
baseline is a set of documents (drawings, schematics, requirements)
that will have changes controlled thru a formal approval process.) Just
as the focus of Pre-Phase A was on the <u>mission</u> and
mission requirements, this focus in Phase A is to produce<u> system</u> level
requirements and a system level architecture. Here
the team drives down the mission requirements to detailed system
specification requirements, such as power voltage levels (i.e. 28
VDC +/- .5 V). Trade
studies are performed to determine the best system for the project
(remember that most likely more than one approach was produced in
Pre-Phase A) , consider the key parameters, i.e. power consumption,
weight, volume, space legacy, costs, etc. to choose the best
approach. Propose the subsystems and anticipated performance of
each, identify major components of the subsystems. Develop
surrogate subsystem modes and run a trade space analysis of the
alternatives. If
necessary apply modeling techniques such
as engineering modeling,
state machines, block diagrams, computer simulations,
proof-of-concept prototypes, mental models, or strawman designs to
compare alternative architectures to home-in on the best. Identify
risks and perform necessary analyses. System
requirements, specifications and schematics are released in formal
documents. Subsystem
budgets are allocated and controlled from this point in time. </b>
</span> </p>
<p>
<b><i>Systems Engineer's Tasks:</i></b> Leads
all Phase A activities with support from subsystems lead personnel.<o:p></o:p></p>
<h3>
<b>11 Systems Engineering Functions</b></h3>
<p>
<i>Input</i></p>
<p>
The input is the output of Pre-Phase A, which includes one or more
high level system architectures, plus mission
requirements and mission
ConOps.</p>
<p>
<i>Architecture and Design Development<o:p><a name="Chap3_PhaseA_A&D_Example"></a></o:p></i></p>
<p class="style14">
Block diagram the system and its subsystems. List
the functions that must be performed by each subsystem and
anticipated performance.</p>
<p>
<i>The team now had enough
information to visualize the next tier systems (or subsystems) that
would be required to meet the requirements and operations concept,
so it develops a Product Breakdown Structure for the Cube Satellite
System or Cubesat System (CSS) to Tier 2 as shown below in Figure
2-5: <o:p></o:p></i></p>
<p>
CSS Systems (Tier 1)<o:p></o:p></p>
<p>
· The
ground station system for sending and receiving signals and
processing data from the cubesat satellite.<o:p></o:p></p>
<p class="style9">
· The
rocket system, which includes Tier 1 systems:<o:p></o:p></p>
<p class="style8">
o The
rocket<o:p></o:p></p>
<p class="style8">
o The
deployer<o:p></o:p></p>
<p class="style8">
<o:p></o:p></p>
<p class="style9">
· For the cube satellite system, which contains Tier 2 subsystems:<o:p></o:p></p>
<p class="style9">
o A <i>communications
system</i> will be needed
to send signals from the satellite to the ground station.<o:p></o:p></p>
<p class="style9">
o A <i>command
and data handling system</i> for
circuit boards, programming and selection of hardware for the
circuit boards.<o:p></o:p></p>
<p class="style9">
o An <i>electrical
power system</i> with a
power supply and power regulators.<o:p></o:p></p>
<p class="style9">
o A <i>mechanisms
and structures system</i> for
satellite cube, mountings and mechanisms for antenna and antenna
deployment.<o:p></o:p></p>
<p class="style9">
o A <i>thermal
system</i> to ensure that
component temperature limits are not exceeded.<o:p></o:p></p>
<p class="style9">
o An <i>attitude
determination and control system</i> for
satellite position and orientation sensing and adjustment.<o:p></o:p></p>
<p class="style9">
o A <i>payload
system</i> to collect and
store voltage signals from the sensor.<o:p></o:p></p>
<p>
Students on the C&DH team
visualized the components for their system:<o:p></o:p></p>
<p class="style7">
C&DH Subsystem (Tier 2):
A microcontroller, a flash drive (perhaps 32 or 64 MB), a PC Bus,
analog to digital converter and general purpose input/output.<o:p></o:p></p>
<p>
<o:p> </o:p></p>
<p>
<img border="0" height="226" src="SiteImageFiles/Chapter3/image024.gif" v:shapes="Diagram_x0020_2" width="632" /></p>
<p>
Figure
2‑5 Architecture
of the Cube Satellite</p>
<p class="style7">
Mechanical Interfaces<a name="ICD_PhaseA"></a>: Launch
vehicle, and cubesat deployer (P-pod) are elements (systems) that
interface with the cubesat. Neither
the rocket nor the cubesat launcher will be designed here.<o:p></o:p></p>
<p class="style7">
Electrical Interfaces: C&DH interfaces to
all systems, Power additionally interfaces to COMM, COMM interfaces
to Ground Station, and payload interfaces to C&DH. <o:p></o:p></p>
<p>
<i>Components were visualized and listed (without detailed
manufactures specifications)<o:p></o:p></i></p>
<p>
2‑1: Table of subsystem major components</p>
<table border="0" cellpadding="0" cellspacing="0">
<tr>
<td nowrap valign="bottom">
<p>
<b>
SYSTEM<o:p></o:p></b></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p></o:p></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p></o:p></p>
</td>
<td nowrap>
<p align="center">
<b>
Satellite<o:p></o:p></b></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p></o:p></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p></o:p></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p></o:p></p>
</td>
</tr>
<tr>
<td nowrap valign="bottom">
<p>
<b>
<o:p>
</o:p></b></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td nowrap valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
</tr>
<tr>
<td nowrap valign="bottom">
<p>
<b>
SUBSYSTEMS<o:p></o:p></b></p>
</td>
<td nowrap>
<p align="center">
<b>
EPS<o:p></o:p></b></p>
</td>
<td nowrap>
<p align="center">
<b>
STRUCTURE<o:p></o:p></b></p>
</td>
<td nowrap>
<p align="center">
<b>
C&DH<o:p></o:p></b></p>
</td>
<td nowrap>
<p align="center">
<b>
COMM<o:p></o:p></b></p>
</td>
<td nowrap>
<p align="center">
<b>
ADC<o:p></o:p></b></p>
</td>
<td nowrap>
<p align="center">
<b>
THERMAL<o:p></o:p></b></p>
</td>
</tr>
<tr>
<td nowrap valign="bottom">
<p>
<b>
<o:p>
</o:p></b></p>
</td>
<td valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
<td valign="bottom">
<p>
<o:p>
</o:p></p>
</td>
</tr>
<tr>
<td nowrap rowspan="3">
<p>
<b>
COMPONENTS<o:p></o:p></b></p>
</td>
<td>
<p align="center">
Power Generator (ex: Solar Cells)<o:p></o:p></p>
</td>
<td>
<p align="center">
Satellite casing<o:p></o:p></p>
</td>
<td>
<p align="center">
Computer memory<o:p></o:p></p>
</td>
<td>
<p align="center">
Transceiver<o:p></o:p></p>
</td>
<td>
<p align="center">
Gravity boom<o:p></o:p></p>
</td>
<td>
<p align="center">
Temperature sensing network<o:p></o:p></p>
</td>
</tr>
<tr>
<td>
<p align="center">
Power Regulators<o:p></o:p></p>
</td>
<td rowspan="2">
<p align="center">
Mechanical systems (ex: Boom release mechanism)<o:p></o:p></p>
</td>
<td>
<p align="center">
Computer controller<o:p></o:p></p>
</td>
<td>
<p align="center">
Antennae<o:p></o:p></p>
</td>
<td>
<p align="center">
Oscillation damping system<o:p></o:p></p>
</td>