This is written for getting the light curves of ZTF transients by forced-PSF photometry.
If you wish to use light curves produced by this code please cite the original paper that describes the real-time pipeline (ZTF Science Data System): Masci et al. (2019), the the paper specifically for this package: Yao et al. (2019, in prep).

ForcePhotZTF performs multiple tasks including:

• downloading images from IPAC
• getting ZTF light curves from the GROWTH Marshal website (Kasliwal et al. 2019)
• getting alert package info from Kowalski (optional)
• running forced photometry on Caltech forced phometry service (fps, Masci et al. 2019), kindly provided by Frank Masci at IPAC. I've compared his result and my ForcePhotZTF result -- they are very consistent with each other. The only difference may be the size of cutout and the assumption in gain factor. Thus, this step is optional. I only want some column information given in the header of sci images, which can also be obtained from fps.

You need to provide your username and password (save them to a file) in the format of username:password. Prepare four txt files:

1. auth_fps.txt
   (If you do not have the access, just print : to this file and do not run the final step shown in the demo)
2. auth_ipac.txt
3. auth_kowalski.txt
   (This is not necessary in any of the main steps. Thus, just print : to this file if you do not have Kowalski access)
4. auth_marshal.txt

Please see demo.ipynb