From the LA Times [latimes.com]:
The launch manifest for Los Angeles-based Rocket Lab is starting to fill up. The small-satellite launch company said Tuesday that it has signed an agreement with Earth-imaging satellite firm Planet for three dedicated launches on its Electron rocket.
The launches will take place from the company's Mahia Penninsula launch site [stuff.co.nz].
SpaceNews [spacenews.com] reports:
[...] each launch will carry is still being determined, but will likely be between 20 and 25. Each Dove is a three-unit cubesat with a mass of about five kilograms.
The schedule for the launches will depend on the development of Electron, which has yet to make its first flight. Safyan said that if the Electron test program goes well, the first Planet launch, likely to sun-synchronous orbit, could be as soon as the second quarter of 2017.
Although the terms of the deal weren't announced, Rocket Lab quotes a price of about $5 million (USD) per launch for the Electron.