UPDATE: the issue described below has now been fixed and the correct list of downloadable files will be reflected in both permissions and the assets list.
The Planet Data API is a little misleading in reporting the presence of
analytic assets when they don't actually exist for a particular item. However, the
_permissions field does report whether you will be able to download an
analytic if you try.
As an example, see https://api.planet.com/data/v1/item-types/PSScene3Band/items/20161015_204122_0c0b.
The permissions are:
This correctly informs you that there is no
analytic asset that can be downloaded. Likewise, although there is an
analytic entry in the response to https://api.planet.com/data/v1/item-types/PSScene3Band/items/20161015_204122_0c0b/assets/, the permissions list there also indicates that you can't download it:
For assets that can be downloaded,
"_permissions" will be set to
An update to the API will make this clearer, by removing the entry for
analytic altogether when it is not available for download.
One other clarifying point, the
analytic_dn asset in the Data API is equivalent to the
analytic from API v0. The
analytic asset in the Data API is a new product (specs in documentation).