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tess-bite

Take a quick bite out of TESS Full Frame Images using HTTP range requests.

pypi

tess-bite is a user-friendly package which provides fast access to sections of TESS Full-Frame Image (FFI) data. It uses the HTTP range request mechanism to download only those parts of an FFI that are required to obtain a cut-out image.

Installation

python -m pip install tess-bite

Example use

Obtain a Target Pixel File for a stationary object:

>>> from tess_bite import bite
>>> bite("Alpha Cen", shape=(10, 10))
TargetPixelFile("Alpha Cen")

Obtain a Target Pixel File centered on a moving asteroid:

>>> from tess_bite import bite_asteroid
>>> bite_asteroid("Vesta", start="2019-04-28", stop="2019-06-28)
TargetPixelFile("Vesta")

Obtain a cut-out image from a single FFI:

>>> from tess_bite import bite_ffi
>>> bite_ffi(url, col=50, row=20, shape=(20, 20))

Quickly download the header of an FFI:

>>> from tess_bite import bite_header
>>> bite_header(url, ext=0)
FitsHeader

What are HTTP range requests?

Tess-bite is powered by the HTTP range request protocol. This is a mechanism which allows a client to request specific bytes from a file on a web server. For example, downloading a 3-by-3 pixel square of 4-byte pixel values from a TESS image can be done very quickly using a HTTP request as follows:

>>> import httpx
>>> url = "https://mast.stsci.edu/portal/Download/file?uri=mast:TESS/product/tess2019142115932-s0012-2-1-0144-s_ffic.fits"
>>> resp = httpx.get(url, headers={"Range": "bytes=80000-80012,80020-80032,80040-80052"})
>>> print(resp.text)

--00000000000000000103
Content-Type: application/octet-stream
Content-Range: bytes 80000-80012/35553600

D�A@DLR½DW˜oD
--00000000000000000103
Content-Type: application/octet-stream
Content-Range: bytes 80020-80032/35553600

³D .]D�ªJD
--00000000000000000103
Content-Type: application/octet-stream
Content-Range: bytes 80040-80052/35553600

D-aöD+W/D�R�D
--00000000000000000103--

Of course the difficult part is to translate pixel coordinates to byte positions, and to convert bytes to pixel values. Tess-bite takes care of these steps for you!

Documentation

Coming soon!

Similar services

TESScut is an excellent API service which allows cut outs to be obtained for stationary objects. Tess-bite provides an alternative implementation of this service by leveraging the HTTP range requests mechanism to download pixel values directly from FFI files.

Compared to TESScut, the goal of tess-bite is provide an alternative way to obtain cut-outs which does not require a central API service, but can instead be run on a local machine or in the cloud. At this time tess-bite is an experiment, we recommend that you keep using TESScut for now!