International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part Bl. Istanbul 2004
communication hardware, the Microhard MHX, this driver
could easily be found for the device and embedded linux.
3.7 Solutions in Payload Integration
The payload in a satellite is the combination of hardware and
software that is there specifically for the purpose of
accomplishing the mission. Payloads are the reason that
missions are flown in the first place and are typically unique to
each mission. The purpose of the rest of the spacecraft, known
as the spacecraft bus, is to accommodate the payloads and keep
it operating within requirements.
The interface between spacecraft bus and payload is usually a
source of considerable costs, since it involves requirements
from several subsystems. For example, the structures
subsystem is typically concerned with the mechanical
attachments and load transfer from payload to bus, the
electrical power system is concerned with the payload's power
consumption and the C&DH subsystem is concerned with flow
of information between bus and spacecraft.
As suggested previously, the development of a standard
structure can bring added benefits outside the structures
subsystem proper. À standard structure can lead to a standard
interface between bus and payload that incorporates
mechanical, electrical, and thermal and data needs into a
ready-to-use solution that fits most missions.
As an example, we examine the CubeSat program. Developed
jointly between the California Polytechnic State University San
Luis Obispo and Stanford University's Space Systems
Development Laboratory, the CubeSat program sets standards
for pico satellites in terms of size, volume, mass, shape and the
interface to the orbital deployer they are launched from (called
the P-POD). Since the P-POD can accommodate three
CubeSats stacked on top of each other, there are some missions
that have taken advantage of this and built satellites that use
the space of two or three CubeSats. Taking this concept à little
bit further, it is conceivable to create a standard way for
CubeSats to interface with each other, so that one CubeSat
becomes the bus and another the payload in a given mission.
The result would potentially make CubeSats even more
popular, making it easier for different groups to cooperate on
projects.
A similar idea can be scaled for use in small satellites but not
quite as small as CubeSats. Creating a standard structure, with
a standard interface between payload and bus can bring
enormous savings, promote the cooperation between different
organizations and even the creation of a commercial niche for
standard spacecraft buses and payloads that can “plug and
play” with each other, in the same fashion as PC components
are mixed and matched today.
4. THE COST OF LAUNCH
The cost of a space mission lies not only in the building and
the operation phase only though. For one part of the mission
every small satellite builder has to go to a bigger company and
that is the launch vehicle that will deliver the finished satellite
into orbit. Right now there are not that many launch vehicle
companies in the world and most of the launches are quite
expensive for the small satellite industry. Most of these
launchers employ complex systems and are based on heritage
technology and require complex procedures to build, maintain
and operate which keeps the overall cost per weight ratio very
high.
February small satellites were dealt another blow when the
loss of the space shuttle Columbia and immediate grounding of
the remaining fleet put at least a temporary end to free rides
for even the smallest hitchhiker payloads.
Yet even in the launcher business there have been some
improvements over the last couple of years which the satellite
industry can count on for the future. One of the mainstays of
the small launch business is Orbital Sciences Corp.'s Pegasus
rocket. At prices of $15 million and up, the Pegasus is often
beyond the reach of experimenters with satellites for small
institutions, yet still can be of use for slightly larger projects.
The European Space Agency plans to spend more than 300
million euros on the development of the Vega small-satellite
launcher. The development is being led by ELV, a joint
venture of FiatAvio of Colleferro, Italy, and the Italian Space
Agency.
The three-stage rocket will be operated from Guiana Space
Center in Kourou, French Guiana, beginning in 2006 and will
be capable of placing a 1,500-kilogram satellite into a 700-
kilometer low Earth orbit.
But the real news is coming from new entrepreneurial
companies opening up in this new business. SpaceX, an El
Segundo, California-based small company of approximately 50
engineers, where the author is also working, is about to finish
their first launcher, the Falcon-I, to be placed in service later
this year. The company, founded by Elon Musk, a 32-year old
serial-entrepreneur who made his fortune on the Internet, looks
forward to offering 450kg LEO launches for no more than $6
million followed by a medium-sized launcher the Falcon-V,
which will deliver up to 9200 pounds to LEO with a fairing
diameter of 4 meters. This vehicle will be also capable of
launching missions to geostationary orbits and the inner solar
system or carring supplies to the ISS with the addition of a
lightweight automated transfer vehicle. With a successful
launch, SpaceX could be providing 10 times the cost efficiency
to the customers of its rockets.
Yet SpaceX is not the only company to enter this new
business. Microcosm Inc., of El Segundo, California also is
seeking to enter the small launch market. Robert Conger,
Microcosm's executive vice president, said the company's
proposed Sprite Small Expendable Launch Vehicle would
carry 700 pounds to orbit for $2.5 million. Development of
Sprite, however, is on hold until Microcosm secures
government funding.
In the meantime, other private efforts, while not aimed
explicitly at the small satellite market, could be a boon for
small satellite proponents. Two dozen private ventures have
emerged to compete for a $10 million purse put up by the St.
Louis-based X-Prize foundation, to be awarded to the first
team to build a piloted vehicle and complete two suborbital
flights within two weeks.
X Prize Chairman Peter Diamandis said that while the primary
market for the suborbital spacecraft is tourism, some X Prize
contestants see an opportunity to launch small satellites with
their vehicles. Any development that promises to change
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