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