Unable to Coregister master and slave using SNAPPY

Hello everyone,

I am attempting to do offset tracking between two different dates. I have successfully been able to assign a master and a slave image in my code, but I am unable to coregister the two images. Please see my code below:

print “Initiating DEM Assisted Corregistration”

print “Reading products to coregister…”
parameters = HashMap()


parameters.put(‘SMaster’, target_0_0)
parameters.put(‘SSlave’, target_0_1)

CoReg = OrbFile_master + “_CoReg”
target_1_0 = GPF.createProduct(“CoregistrationOP”, parameters, target_0_0)
ProductIO.writeProduct(target_1_0, Coreg, ‘BEAM-DIMAP’)

The error is being initiated at the GPF.createProduct line. The error I am getting is:

RuntimeError: java.lang.NullPointerException

Can anyone help me figure out where I am going wrong? The images are currently not stacked when starting the process, do you think this is the issue?