Download 1. Mars or Bust! - Computer Science

Remote Monitoring of a Heterogeneous Sensor Network for
Biomedical Research in Space
Keywords: sensor network, microgravity, space station, biomedical research
Kathy J. Liszka ** presenter / contact
The University of Akron
Dept. of Computer Science
Akron, Ohio 44325-4002
(On site at NASA Glenn Research Center)
Office: (216) 433-5110
Fax: (216) 433-8000
[email protected]
David W. York
NASA Glenn Research Center
MS 86-11
21000 Brookpark Road
Cleveland, Ohio 44135
Office: (216) 433-3162
Fax: (216) 433-8000
[email protected]
Michael A. Mackin
NASA Glenn Research Center
MS 86-11
21000 Brookpark Road
Cleveland, Ohio 44135
Office: (216) 433-5326
Fax: (216) 433-8000
[email protected]
Michael J. Lichter
NASA Glenn Research Center
MS 86-5
21000 Brookpark Road
Cleveland, Ohio 44135
Office: (216) 433-8588
Fax: (216) 433-8000
[email protected]
Abstract
The objective of this research is to
present the design and development of a
heterogeneous sensor network and remote
experiment server with personality modules
to service microgravity research in
biomedical engineering. We present the
architecture for cardiac, metabolic and
ocular research to be conducted on the
International Space Station. The purpose of
this project is to assess, understand,
mitigate, and manage the risks associated
with long-term exposure to the space
environment. It is anticipated that the
ground-based, spin-off use of the
experiments will contribute to the
improvement of health care for the people
on Earth.
1. Mars or Bust!
NASA has launched astronauts into
space for more than four decades. Alan
Shepard’s historical flight in 1961 lasted 15
minutes 22 seconds. Skylab was home to
three crews from 1973-74, the longest
lasting 84 days, proving that humans could
potentially live and work in space for
extended periods. However, this was not
enough to even begin to assess long term
effects of microgravity on humans. It wasn’t
until 1995 when a succession of seven
astronauts joined Russian cosmonauts on the
MIR space station, that we had the
opportunity to begin serious research on
how to sustain long-term space expeditions
in preparation for permanent operations on
the International Space Station (ISS).
Significant studies on human adaptation to
space have been conducted on the Space
Shuttle, but long term scientific data cannot
be collected in this manner. Missions are
limited to roughly two weeks because of the
effects of microgravity on the vestibular
system that regulates the body’s equilibrium.
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The shuttle is a reusable launch vehicle
requiring a piloted landing operation.
Somewhere between the third and fourth
weeks, the accumulated effects of
microgravity alter an astronaut’s perception
of spatial orientation enough to make
manual landing maneuvers too risky to
attempt.
When Expedition One docked at ISS in
November 2000, it marked the beginning of
a new era of space exploration with a
permanent human presence in space. Today,
while orbiting the earth at an average
altitude of 354 kilometers (220 miles) for up
to six months at a time, astronauts defy a
hostile, oxygen-less environment of freezing
temperatures and lethal radiation levels. Yet
in order to embark on the long-term
missions suggested in the current
Administration’s new agenda, we must
overcome additional hurdles that keep us
earthbound. NASA has been tasked to
extend human presence across the solar
system, starting with a human return to the
Moon by the year 2020 in preparation for
human exploration of Mars and other
destinations. Our primary concern is the fact
that prolonged exposure to microgravity will
cause major physiological changes to the
human body.
The John Glenn Biomedical Engineering
Consortium (JGBEC) focuses on health
related countermeasures for astronaut crews.
Project Rescue, a part of JGBEC, serves two
purposes. The first is to design and build a
space-based specialized sensor network for
embedded, real-time systems to support
biomedical experiments that can be
monitored and/or controlled either locally or
remotely. The second objective is a
biomedical experiment that concentrates on
studying electrophysiological changes in the
heart as a way to understand how the body’s
conduction system works.
2. Architecture
The system objective of Project Rescue
is to provide an interoperable framework for
accessing and controlling sensor and sensor
systems in space via standard web protocols.
Figure 1 shows the basic on-board
configuration. Two experiments in addition
to Rescue have been identified to work with
the system. PUMA measures metabolism
with a portable unit, which can be carried by
the human subject. INI-Tech looks for
physiological anomalies through various
non-invasive examinations of the eyes.
Sensor data is transmitted via a shorthaul network to a personality module
processor dedicated for that experiment. A
serial link with standard connections will be
immediately
implemented.
Wireless
transmission is the ultimate goal but may not
be available for the first experiment because
it is subject to stringent safety requirements.
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ISS is a closely monitored environment with
many
hardware,
software
and
communication systems on board. Their
interactions and potential conflicts with each
other must not impact the safety of the crew
or station.
The personality module is a processor
board with enough storage for up to 6 hours
of archived data. Incorporating new sensors
can be done almost seamlessly and without
reengineering the design. This module is
responsible for running algorithms and
signal analyses unique to their sensor
measurements. Installed in each module is
an embedded web server with stored HTML
and embedded Java applets for remote
command and telemetry access. The boards
plug into a CompactPCI backplane, a high
performance industrial bus based on the
standard PCI electrical specification in
rugged 3U or 6U packaging. Personality
modules are inserted from the front of the
chassis.
The experiment processor is the contact
point for the system and is responsible for
the remote access protocols to and from the
ground facilities. Astronauts will be able to
plug a laptop computer directly into the
system to give commands and retrieve data
for each experiment. The experiment
processor provides functions common to all
personality modules. These include long
term (greater than 4 days) archival of data,
Embedded Web Technology (EWT) and a
communications interface to the spacecraft
TCP/IP or CCSDS1 data link [1]. A
researcher is not constrained by operating
system or hardware requirements to
remotely interact with their experiment. We
only require a connection to the network
with a standard network card and a standard
Web browser. Command and telemetry links
to the personality modules are available as
URLs.
The experiment processor is designed
for mounting in a Lab standard payload rack
or an Express rack. Figure 2 shows the
communication paths from Project Rescue
to the scientists on the ground. Digital
sensor data is packetized at the application
level on the personality modules. The
experiment server holds the packets until
data downlink is scheduled based on
availability of bandwidth of the Tracking
and Data Relay Satellite System (TDRSS)
and Space Station resources.
The Space Station Command and Data
Handling system (C&DH) is comprised of
several
components
with
different
operational capabilities and objectives [2].
The experiment server will provide
1
CCSDS (Consultative Committee for Space
Data Systems) is the protocol used for spacebased telemetry handling. According to the ISS
OD/Avionics and Software office of ISS,
conversions from CCSDS to TCP/IP, Phase 2, is
scheduled for completion in May 2005.
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communications hardware and software
interfaces compatible with the ISS Medium
Rate Data Link (MRDL), an Ethernet local
area network provided for telemetry.
The TDRSS system uses two
geosynchronous satellites for space-toground communications. The Ku-band
communication link operates at 43.2 Mbps
and is used for transmission of video and
high-speed data to earth. The S-band
communication link operates at 57 Kbps.
This link is used for transmission of twoway voice commands to the space station
and telemetry from the space station to the
ground. Once on the ground, the Payload
Data Services System (PDSS) at Marshall
stores and distributes the data to experiment
principle investigators running a thin client.
3. Biomedical Sensors
A plethora of biomedical sensors are
available to detect and measure physical,
chemical and biological phenomena. Their
use in space has yielded varying degrees of
success. The sensor systems selected for
Project Rescue are not tiny, certainly not on
the scale of motes2, but they are reasonably
portable. Size and weight are significant in
light of the cost to send payloads to the
Space Station, sharing precious space
packed with food, water and oxygen.
Astronaut mobility in tight quarters is
another factor.
The experiment most likely to be
manifested for flight first is the cardiology
part of Rescue. This is, in part, due to the
fact that the special ECG unit made by
Cambridge Heart, a partner in this project, is
already available. Medical protocols have
already been developed for the experiment
by cardiologists at the MetroHealth Campus
of Case Western Reserve University.
2
A mote is a tiny electronic device that contains
a tiny computer, radio, sensors and a power
supply.
Another consideration is the time and effort
to install and test the communication system
before loading the rest of the personality
modules. PUMA and INI-Tech are NASA
technology still under test and development.
3.1 Rescue: T-Wave Alternans
Rosenbaum, et. al., [5] established the
significance of T-wave alternans (TWAs) as
a predictor of life threatening cardiac
arrhythmia. Cardiologists are unsure how
these affect the electrical activity of the
heart on return to earth. What they do know
is that the heart changes electrically as a
function of time in orbit. In basic terms, the
heart is simply an electrically controlled
mechanical pump. Electrical activity
normally spreads out in an organized
manner. If this pattern is disturbed, due to
functional or anatomical blocks, an
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arrhythmia results that can be lethal if left
untreated. More commonly known as a
sudden heart attack, it is the one of the more
common causes of death in the United
States.
Now consider an astronaut after 30 days
of prolonged exposure to microgravity. The
heart has become larger, thinner, and as the
result of other physiological changes, pumps
less efficiently and does not get enough
blood. Flight surgeons also know that the
heart changes electrically as a function of
time in orbit. Astronauts have experienced
episodes of cardiac arrhythmias (an
abnormal rhythm of the heart beat) in space
[3, 4]. This is extremely dangerous, as it can
result in brief loss of consciousness,
endangering the whole crew and
compromising successful completion of a
mission.
The Cambridge Heart unit will be used
to detect microvolt TWAs and prolonged
QT intervals. It uses a 14-lead ECG sensor
lead-set (7 conventional, 7 multi-segment),
generating 32 channels of data. All standard
ECG measurements can be derived from this
configuration as well. Historical ECG data
collected from astronauts has had
questionable value because the heart shifts
in location in addition to the other changes
experienced in orbit. The orthogonal lead
system on this unit mitigates those effects so
that lead placement on the body does not
have to be as accurate in order to make
comparable measurements over a time
series. The personality module built for this
experiment will contain TWA signal
analysis software supplied by Cambridge
Heart.
The purpose of the first flight will be to
prove that we can make the required
microvolt measurements, analyze, store and
transmit the resulting data to researchers on
the ground. When this is confirmed, longterm signal collection will provide medical
researchers with a way to understand how
the conduction system works as a function
of microgravity and time in flight. If this can
be done, then it may be possible to create
and deploy effective counter-measures for
astronauts who may, for example, be on the
moon 239,000 miles away. It may also be an
effective screening tool for selection of
astronauts for long terms missions in the
future.
3.2 PUMA
Astronaut fitness is a major concern for
NASA, especially during longer duration
missions. Without the natural loading of
gravity, bones and muscles weaken, causing
problems when crewmembers return to
earth. Studies of MIR and ISS missions
reveal a reduction in bone mass at the rate of
1 to 1.5% per month [6]. Although the
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metabolic function is measured on
astronauts to collect data, it requires a large,
cumbersome and stationary set of
instruments to which the crew must literally
be attached to with tethers. Dietrich, et. al.,
[7] are developing a Portable Unit for
Metabolic Analysis (PUMA) that will
quantify metabolic function by measuring
temperature, flow, and pressure during
respiration using prototype oxygen, CO2 and
flow sensors. The portable device will
enable measurements during various crew
activities without tethers when the wireless
portion of the communication interface to
the personality module is implemented.
3.3 INI-Tech
Radiation probably poses the greatest
danger to astronauts. We are protected on
Earth because the magnetic field attenuates
its harmful effects. Increased exposure to
cosmic radiation during long duration space
exploration damages the basic cell DNA
structure and causes gene mutation. Even
relatively low doses of radiation cause an
increased risk of retinal detachment and
cataracts. Ansari, et. al., [8] have developed
and are testing an instrument that will detect
early, subtle signs of changes in the fluids,
tissues, and blood vessels of the eye and
brain. Noninvasive optical measurements
have the potential to provide health indices
not just for these organs, but also for the
entire body. Resembling night-vision
goggles, the apparatus will house
miniaturized fiber optic probes to collect
health data that may detect ocular and
systemic abnormalities long before clinical
symptoms appear.
4. Becoming Flight-worthy
Before something can fly on a Shuttle or
the Space Station, it must undergo a lengthy
process of modification and testing.
Although the prototype Rescue system is not
intended for flight, it will, where practical,
be designed with spaceflight environment
requirements relating to electromagnetic
interference and compatibility (EMI/EMC),
vibration, microgravity effects, packaging,
training and launch loads. The fidelity of
this system will be equivalent to an
Engineering Model (form, fit, and function).
The design goal is to produce a system
which can be qualified for flight with minor
modifications.
Hardware problems that may occur must
be anticipated and allowed for. Software
must also run reliably, and be reconfigurable
from the ground. In short, whether you are
orbiting the earth at 250 miles or on your
way to Mars, consistency and reliability is
the best choice every time!
 INI-Tech: Perhaps the most diverse
experiment, additional benefits on earth,
include early detection of changes in the
eye associated with infection, allergic
reactions, autoimmune diseases, glaucoma,
age-related macular degeneration, and
diabetic
retinopathy.
Early
cataract
formation and diabetes diagnosis can also be
detected using this technology.
5. Down to Earth
We are grateful to Dr. Leslie R. Balkany, for
his editorial and technical comments. The
John Glenn BioEngineering Consortium at
the NASA Glenn Research Center funded
this work.
In our quest to explore an inhospitable
universe, we improve the quality of our lives
on
earth.
Science,
medicine,
and
communications
have
benefited
tremendously from NASA funded research
programs. These experiments will be no
exception.
 Rescue: An earth-based system would
allow patients to be monitored for
arrhythmias in near real time outside the
hospital. Patients become mobile, continuing
their daily lives at home, at work and on the
road. This technology could potentially save
many lives each year.
 PUMA: Convalescing patients could use
the portable metabolic measurement device
to measure their physical response to
exercise. Athletes in training could increase
their endurance by making ensuring their
workout keeps them working at the top of
their
capacity.
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A crewed mission to Mars currently lies
outside
of
our
technological
and
physiological abilities. We know that Project
Rescue can contribute to the realization of
this ambition by providing the network and
communication infrastructure to advance
research with new and unique sensors.
6. Acknowledgements
7. References
[1] Ponyik, J. G. and York, D. W.,
“Embedded Web Technology: Applying
World Wide Web Standards to
Embedded Systems,” NASA TM-2002211199,
AIAA-2001-5107, March 2002.
[2] Mortonson, M. W., “ISS Enhanced
Payload Data Network for International
Space Station utilization on-orbit,” AIP
Conference Proceedings, Jan. 2000, vol.
504(1) pp. 649-654.
[3] Baisden, D. L. and Jones, M. M.,
“Cardiac Dysrhythmia Analysis on
Flights STS-1- STS 61C,” Houston
NASA, 1988.
[4] Fritsh-Yelle, J. M., Rossum, A. C.,
Brown, T. E., Leuenberger, U. A.,
D’Aunno, D. S., Josephson, M. E. and
[5]
[6]
[7]
[8]
Goldberger, A. L., “An episode of VT
during long duration spaceflight,”
American Journal of Cardiology, 1998,
81:1391-92.
Rosenbaum, D. S., Jackson, L. E.,
Smith, J. M., Garan, H., Ruskin, J. N.
and Cohen, R. J., “Electrical alternans
and
vulnerability
to
ventricular
arrhythmias,” New England Journal of
Medicine, Jan 27, 1994, 330:235-41.
Turner, R. T., “Physiology of a
Microgravity Environment: Invited
Review: What do we know about the
effects of spaceflight on bone?,” J. Appl.
Physiology, Aug. 2000; 89: 840 - 847.
Dietrich, D., Piltch, N., Cabrera, M.,
Struk,
P.,
and
Pettegrew,
R.,
Development of a Portable Unit for
Metabolic
Analysis
(PUMA),
http://microgravity.grc.nasa.gov/grcbio/f
itness.html.
Ansari, R. and Carbrera, M., Integrating
Non-Invasive Technologies to Enable
Effective
Countermeasures
during
Prolonged
Space
Flight,
http://microgravity.grc.nasa.gov/grcbio/e
ye.html.
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