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| Deletions are marked like this. | Additions are marked like this. |
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| The MSIS static density model uses these double precision variables: | The MSIS-86 static density model uses these double precision variables (with scal added, if I can take a derivative in the code): |
| Line 13: | Line 13: |
| || sf[2] || averaged daily flux, Jensen || | || sf[2] || averaged daily flux, Jensen same input as sf(1) || |
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| || tp[1] || exospheric temperature, Kelvin || || tp[2] || local temperature, Kelvin || || ad[1-6] || log10 number densities, He, O2, N2, Ar, O, H || || wmol || mean molecular weight || || dens || thermospheric density, kg/m3 || |
|| tp[1] || exospheric temperature, Kelvin (INFO ONLY) || || tp[2] || local temperature, Kelvin (IGNORED FOR NOW) || || ad[1-6] || log10 number densities, (IGNORED FOR NOW) || || wmol || mean molecular weight (IGNORED FOR NOW) || || dens || thermospheric density, kg/m3, used for drag model || || scal || scale height, meters (ADDED), used for drag model || |
Exosphere Models
Exosphere
Production server sky orbits will be at 6411 kilometer altitude, or above, far into the exosphere. Such high orbits offer little detectable drag to big iron satellites, so their densities are characterized indirectly and perhaps imprecisely above 1000 km altitudes. Thinsats have much higher "sail" ratios and are more sensitive to density.
There are many high altitude atmospheric models, evolving from Jacchia64. Here is an online model from NASA, based on MSIS-E-90 and valid to 1000 km altitude. The most useful model for our purposes (above 120 km) is the MSIS-86 model. For estimation, we will use MSIS-86 with static density and F10.7 daily solar fluxes of 70 (minimum), 120 (average), and 200 (maximum) x10-22W/m2Hz. In the past, F10.7, has cycled from low to high and back with an 11.5 year period. The geomagnetic index Kp is a "kinda logarithmic" number ranging from 0 to 9, near zero at quiet times, probably above 10 for a 500 year Carrington Event. Assume low/middle/high of 0.4, 2, 5.5 (5%, 50%, 95% percentile).
The MSIS-86 static density model uses these double precision variables (with scal added, if I can take a derivative in the code):
inputs |
|
alt |
local geocentric altitude, 90000 to 2000000 meters |
sf[1] |
daily solar flux F10.7, Jensen |
sf[2] |
averaged daily flux, Jensen same input as sf(1) |
sf[3] |
3 hourly planetary geomagnetic index Kp |
outputs |
|
tp[1] |
exospheric temperature, Kelvin (INFO ONLY) |
tp[2] |
local temperature, Kelvin (IGNORED FOR NOW) |
ad[1-6] |
log10 number densities, (IGNORED FOR NOW) |
wmol |
mean molecular weight (IGNORED FOR NOW) |
dens |
thermospheric density, kg/m3, used for drag model |
scal |
scale height, meters (ADDED), used for drag model |