If you use the Subscriptions API and want a specific generation of PlanetScope satellites, you can filter for a specific instrument type when you set up a subscription.

Use the following snippet

 "parameters": {
          "filter": {
            "type": "StringInFilter",
            "config": [
              "PSB.SD"
            ],
            "field_name": "instrument"

and add it to your regular subscription setup, as in the following example:

{
    "name": "Recurring Subscription",
    "source": {
        "type": "catalog",
        "parameters": {
          "filter": {
            "type": "StringInFilter",
            "config": [
              "PSB.SD"
            ],
            "field_name": "instrument"
          },
            "geometry": {
                "coordinates": [[[139.5648193359375,35.42374884923695],
                                [140.1031494140625,35.42374884923695],
                                [140.1031494140625,35.77102915686019],
                                [139.5648193359375,35.77102915686019],
                                [139.5648193359375,35.42374884923695]]],
                "type": "Polygon"
            },
            "start_time": "2021-03-01T00:00:00Z",
            "end_time": "2023-11-01T00:00:00Z",
            "rrule": "FREQ=MONTHLY;BYMONTH=3,4,5,6,7,8,9,10",
            "item_types": ["PSScene"],
            "asset_types": ["ortho_analytic_4b"]
        }
    },
    "delivery": { ... }
}

Read more in the Planet developer documentation.