Editing Solar sail (section)

===Satellites===
[[Robert L. Forward]] has commented that a solar sail could be used to modify the orbit of a satellite about the Earth. In the limit, a sail could be used to "hover" a satellite above one pole of the Earth. Spacecraft fitted with solar sails could also be placed in close orbits such that they are stationary with respect to either the Sun or the Earth, a type of satellite named by Forward a "[[statite]]". This is possible because the propulsion provided by the sail offsets the gravitational attraction of the Sun. Such an orbit could be useful for studying the properties of the Sun for long durations.<ref name=ESA/> Likewise a solar sail-equipped spacecraft could also remain on station nearly above the polar [[terminator (solar)|solar terminator]] of a planet such as the Earth by tilting the sail at the appropriate angle needed to counteract the planet's gravity.<ref name=ESA>{{cite journal | journal= ESA Bulletin |volume=98 | date=1999 | title=Solar Sails for Space Exploration – The Development and Demonstration of Critical Technologies in Partnership |author=M. Leipold, D. Kassing, M. Eiden, L. Herbeck | url=https://www.esa.int/esapub/bulletin/bullet98/LEIPOLD.pdf}}</ref>

In his book ''[[The Case for Mars]]'', [[Robert Zubrin]] points out that the reflected sunlight from a large statite, placed near the polar terminator of the planet Mars, could be focused on one of the Martian polar ice caps to significantly warm the planet's atmosphere. Such a statite could be made from asteroid material.

A group of satellites designed to act as sails has been proposed to measure [[Earth's Energy Imbalance]] which is the most fundamental measure of the planet's rate of [[global warming]]. On-board state-of-the-art [[accelerometer]]s would measure shifts in the pressure differential between incoming solar and outgoing [[thermal radiation]] on opposing sides of each satellite.   Measurement accuracy has been projected to be better than that achievable with compact [[radiometry|radiometric]] detectors.<ref>{{cite journal |last1=Hakuba |first1=Maria Z. |last2=Stephens |first2=Graeme L. |last3=Christophe |first3=Bruno |last4=Nash |first4=Alfred E. |last5=Foulon |first5=Bernard |display-authors=et al |title=Earth's Energy Imbalance Measured From Space |journal=IEEE Transactions on Geoscience and Remote Sensing |year=2019 |volume=57 |issue=1 |pages=32–45 |doi=10.1109/TGRS.2018.2851976|bibcode=2019ITGRS..57...32H |s2cid=57192349 |url=https://hal.archives-ouvertes.fr/hal-01870008/file/DFIE17094.1535440400_postprint.pdf }}</ref>