# IMLEO orbit height

Initial Mass in Low Earth Orbit is a well defined cost metric for space missions [1].

However, this is somewhat subjective since it depends on the orbit height. My guess is that there is a conventional height used for the calculation of IMLEO, but so far I've found nothing on this matter. Everyone seems to use IMLEO, but no one mentions which height is used.

Has someone come across this value? Any relevant information, with the corresponding source, is highly appreciated.

[1] E. D. Ward, R. R. Webb, and O. L. deWeck. A method to evaluate utility for architectural comparisons for a campaign to explore the surface of mars. Acta Astronautica, 128:237 – 242, 2016. ISSN 0094-5765. doi: https://doi.org/10.1016/j.actaastro.2016.07.022. URL http: //www.sciencedirect.com/science/article/pii/S0094576516301904.

• To quote myself: "The only thing all definitions of LEO have in common is that the altitudes are usually much smaller than the radius of the Earth. Which, to me, seems like as good as a definition as any other." c.f. space.stackexchange.com/questions/46353/… Commented Oct 13, 2020 at 17:48

My guess is that there is a conventional height used for the calculation of IMLEO

Standards! Oh yes, we have dozens of those!

Cost varies somewhat between various LEO altitudes. Not a lot, but some. But more importantly, it's a constraint that the launcher is responsible for.

The whole point of IMLEO is to abstract away launch constraints. So really, you just pick an altitude, and say "I need 100 tons here".

Or stated in another way: The precision of an IMLEO simplification is already lower than the precision problems of a fuzzy LEO altitude.

If you want greater accuracy, the LEO altitude must be specified.

Altitudes I have encountered so far:

• 100 km
• 200 km
• 212 km (orbital velocity of 7,777 m/s)
• 222 km (orbital radius of 6,600km)
• 250 km
• 300 km
• 400 km
• 500 km

Within specific organisations, or among certain groups of researchers, this altitude may be well defined and consistent, but this is not universally true.