Understanding PlanetScope Instruments

PlanetScope imagery products are now derived from three cohorts of satellites, with instrument IDs of PS2, PS2.SD, and PSB.SD.

The PS2 Instrument

Planet achieved Mission 1 after the successful launch of 88 Dove satellites in February 2017 and the successful launch of a further 48 Dove satellites in July 2017. This groundbreaking feat enabled Planet to image the world’s land mass, roughly 150Mkm2, every single day in 4 spectral bands: blue, green, red and near-infrared (NIR).

These Dove satellites carry instruments comprised of a telescope we call "PS2" paired with a 2D frame detector having 6600 pixels across by 4400 lines down. The detector has a Bayer pattern filter separating the wavelengths of light into blue, green and red channels. On top of the Bayer pattern filter is a “2-stripe” filter, where the top half blocks the NIR wavelengths, thus allowing only the blue, green and red light to pass through, and the bottom half allows only the NIR wavelengths of light to pass through.

The result is that each frame acquired by the PS2 instrument consists of a top half that is an RGB image and a bottom half that is an NIR image (as seen below). The RGB half of each frame is then combined with the NIR half of the adjacent frame in order to generate the resulting 4-band image.

The PS2.SD Instrument

The PS2.SD instrument is comprised of the same "PS2" telescope and the same 2D frame detector as used in PS2. The Bayer pattern filter and pass-band filters in the PS2 satellites have been replaced with a high-performance butcher-block filter. The PS2.SD filter is made up of 4 individual pass-band filters, that separate the light into each of the blue, green, red and NIR channels. The choice of the pass-band filters for PS2.SD match closely with and are interoperable with those of Sentinel-2. We’ve named this new instrument PS2.SD.

Each frame acquired by the PS2.SD instrument is comprised of 4 stripes, as seen below. In order to generate the final 4-band image, we stack together a number of consecutive frames on either side of a given frame.

The PSB.SD Instrument

The new PSB.SD instrument is comprised of the next-generation "PSBlue" telescope with a larger 47 megapixel sensor and the same filter response as PS2.SD above, in the Red, Green, Blue and NIR bands.

The PSB.SD payloads extend on this capability so that in addition to the four bands that are identical to the PS2.SD spectral bands above (Red, Green II, Blue and NIR), there is also an additional band. Specifically, Red Edge, which is meant to be interoperable with Sentinel-2 band 5. Please refer to the table below in this section to see absorption range for each band.

Band Name Wavelength (fwhm) Interoperable with Sentinel-2
1 Blue 490 (50) Yes - with Sentinel-2 band 2
2 Green II 565 (36) Yes - with Sentinel-2 band 3
3 Red 665 (31) Yes - with Sentinel-2 band 4
4 Red edge I 705 (15) Yes - with Sentinel-2 band 5
5 NIR 865 (40) Yes - with Sentinel-2 band 8a

Please refer to this CSV for spectral response within absorption ranges.

There is a new larger sensor on the PSB.SD payload, meaning that the framing of scene products will be larger in both directions when compared to PS2.SD and Dove Classic scene products.