Resolve "Error when using orbit files v2.0"

Closes #82 (closed)

• Fix the issue with orbit files v2.0
• Avoid printing multiple warnings for orbit files in a development version
• Add unit tests for various orbit files

lisainstrument/instrument.py

@@ -1547,9 +1547,11 @@ class Instrument:
         logger.debug("Solving iteratively (tolerance=%s s, maxiter=%s)",
             self.clockinv_tolerance, self.clockinv_maxiter)
 
-        niter = 0
+        # Drop samples at the edges to compute error
+        edge = min(100, len(timer_deviations) // 2 - 1)
         error = 0
-        edge = 100 # drop samples at the edges to check convergence
+
+        niter = 0
         next_inverse = timer_deviations
         while not niter or error > self.clockinv_tolerance:
             if niter >= self.clockinv_maxiter: