Life cycle costs for FORTRAN+Ada vs. Ada

[cis.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!aero.org!jordan@ucbvax.B erkeley.EDU (Larry M. Jordan)]

Omnes,

I need some references or a summary of findings which address the
life cycle costs of choosing a hybrid (FORTRAN+Ada) vs.
an all Ada effort in scientific applications. 

Here's a bit of background:

A Contractor wants to use FORTRAN to develop some Scientific software.
These scientists (not SEs) are well versed in FORTRAN.  The software
they write will transition to operational software eventually.  That
software is mandated in Ada.  I don't know amount of FORTRAN code
that has to be developed (1K, 10K, 100K SLOC?).

Is it "reasonable" to:

[1] Develop in FORTRAN and "migrate" to Ada?
    o Is conversion/translation of the developed FORTRAN to Ada viable?
    o Or is it better to have a trained Ada programmer to reimplement
      from "language independent" algorithmic descriptions of working
      code?

[2] Or, Require the untrained to develop in Ada from the start? 
    o Take an initial productivity hit an train scientists in Ada?
    o And/Or have a knowledgable Ada programmer(s), who might be
      unfamiliar with the applications area,  work closely with
      the scientists, monitoring what's going on to guarantee "good"
      Ada?

I'd appreciate any lessons learned from practical experience.  I
want to know what works, not what "might" work (I can speculate, too).

What kind of "resistance" can be expected?  Is there any merit to the
counter that "Ada is not a numerical" language?  (I've done no
number crunching in Ada).

Thanks in advance,

--Larry %)