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Airborne Large Aperture Telescope & LTA Platform

- Platform dimensions for existing hangars & reasonable drag coefficient: Diameter = 40 meters; length = 182 meters; total volume = 170,000 cubic meters; available lifting gas volume = 165,000 cubic meters; total lift @ sea level = 154 metric tons.

- Preliminary mass properties estimates (metric tons):
Composite structure & rigging=7; envelope > 4; ballonets=1; primary propulsion=3; secondary propulsion=0.5; power generation=3; flight management & avionics=0.3; two telescopes=3; telescope and T&C instrumentation with environmental control=1.1.
Total = 22.9

The probable ceiling for the specified platform and proposed payload if built with existing technology will probably be at ~0.15 density, or ~16 km altitude. This altitude in the upper tropopause is below most of the equatorial ozone concentration, but it is also below some cirrus clouds and the turbulence ceiling of powerful storms. This will impose certain restrictions:

- The mid-latitude jet stream (i.e. polar front jet stream) will have to be avoided, limiting long term platform deployment to polar regions and/or latitudes within ~35 deg. of the equator.
- Large equatorial storm systems will have to be avoided.

- It is preferrable to deploy ALAT in the lower stratosphere (20-23 km altitude) anywhere in the world. This is above convection and nearly all types of clouds. A ceiling of ~23 km (for reliable use at 20~22 km) is the goal which should ultimately be achieved. This presents additional challenges:

- Rarefied air and corrosive chemicals at high altitude increase cost of achieving a higher ceiling.
- Lifting gas volume / platform ratio will have to be increased; for the same payload mass, total platform volume may have to be increased ~250% over that shown above. Payload and support structure mass is critical.
- Noctilucent clouds can still influence observations.
- Plasma events above storms may be observed from the platform, but their influence on the platform and its payloads is largely unknown.

- Preliminary mass properties estimates for additional functions when integrated into ALAT and its platform:

Airbirne Relay for Deep-Space Optical Communication (ARDOC)=0.3; High Precision Imaging & Ranging of Sattelite & Orbital Debris Tracking (HOST)=0.1; high altitude atmospheric & environmental observation=0.3; optical and other surveillance (0.75m aperture)=0.5; forestry & mapping=0.1; secure air-ground optical communications=0.2; public cellular communications(STRATOCOM (TM))=0.4; public television and other broadcasting=0.3; deep-space RF communications with inflatable reflectors > 0.5; beamed power development & use=0.6; regional position reference (smart maps, etc.)=0.2.


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