How to halfway hide a planet (or make it obvious instead)

In Kipping & Teachey (2016), the possibility of using lasers to modify one’s planetary signature from a transiting exoplanet experiment is discussed.

Advanced civilizations may have several reasons for which they might want to modify their planetary signal. You can use lasers to make your transit either more or less remarkable, but it depends on the type of survey you are trying to adapt to. For broadband surveys like Kepler, it can be a lot easier. If you somehow knew the frequency band of the survey you were trying to hide from, you could use a monochromatic laser near the peak efficiency to effectively modify your planet’s signature. For example, we could hide Earth from a Kepler-like mission with ~30 MW of peak power for ~10 hours a year (the duration of our transit). It gets harder to completely hide a planet for missions that take spectra, as you need many lasers (at least a comparable amount to the number of frequency bins the survey uses) and they need to produce the entire spectrum of energy instead of focussing on the most efficient detector energy (which you probably wouldn’t know anyway). For the Earth, this would require ~250 MW of peak power. I don’t really see the point of doing this when the civilization would still probably find you based on RV data or orbital analyses of the rest of the planets in the system.

Something more interesting you can do is to just mask the atmosphere or even just the biosignatures so that Earth looks barren and uninteresting. This would take considerably less power (~1 MW for the atmosphere, or ~160 kW to mask a couple emission lines).

You could also use about 1/100th of the energy of any of these methods to modify only the begging and end of the transit to create an otherwise impossible transit shape. In this way, you could quite effectively broadcast the fact that there is life on your planet. I find it more likely that ETI would use lasers for this purpose than as a glorified invisibility cloak.