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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