Subject: [ids.analysis.forum] Radiation Pressure Modelling on TOPEX/Poseidon
From: Frank Lemoine <[email-masked]>
To: <[email-masked]>
Cc: "John C. Ries" <[email-masked]>, Jean-Paul Berthias <[email-masked]>, Luca Cerri <[email-masked]>, Eelco Doornbos <[email-masked]>, Marek Ziebart <[email-masked]>, "Luthcke, Scott B. (GSFC-698.0)" <[email-masked]>, Michiel Otten <[email-masked]>, Eric Leuliette <[email-masked]>, Flavien Mercier <[email-masked]>, Remko Scharroo <[email-masked]>, Nikita Zelensky <[email-masked]>, FRANK G LEMOINE <[email-masked]>
Date: Thu, 4 Mar 2010 15:19:17 +0000

Dear All-

Re: the comments this morning on the radiation pressure modelling for 
TOPEX/Poseidon, it is probably
worthwhile to remind everyone what we used in the TOPEX GDR's, as 
documented in the JGR paper of
Marshall et al. (1995).

1. Peter Antreasian as part of his PhD thesis with his advisor George 
Rosborough performed a detailed
micromodel analysis of TOPEX (pre-launch). This is documented in

Anteasian, P.G. and G.A. Rosborough (1992), Prediction of radiant energy 
forces on the TOPEX/Poseidon
spacecraft, J. Spacecraft Rockets, 29, pp. 81-90.

2. Andy Marshall and Scott Luthcke developed a computationally efficient 
representation suitable
for use in an orbit determation program (GEODYN), ie the box-wing model. 
The model includes
fitted and tuned values of the diffuse & specular reflectivities of the 
s/c surfaces, the mean surface
emmissivities, and temperature functions and delay times to accommodate 
heating and cooling
effects.

Marshall, J.A. and S.B. Luthcke, Radiative force model performance for 
TOPEX/Poseidon precision
orbit determination, J. Astronautic. Sci., 49, pp. 229-246.

3. The a priori macromodel was re-tuned by Marshall et al., (1995) just 
before we switched and
froze the second-generation (repro2) modelling standards for the TOPEX 
GDR's.

Marshall, J.A., Zelensky, N.P., Klosko, S.M., et al., The temporal and 
spatial
characteristics of TOPEX/Poseidon radial orbit error, J. Geophys. Res., 
100(C12),
pp. 25331-25352, 1995.

4. The TOPEX macromodel does not accommodate self-shadowing or any 
(potential) warping of the
solar array as discussed, and moreover no correction is made for 
potential changes to the CG location
due to solar array motion. Also, the macromodel is not as sophisticated 
as the University of College
London (UCL)-type models (Ziebart et al., 2005) that we use for Jason 
(at least in the GSFC orbits),
which naturally accommodate self-shadowing and surface thermal interactions.

Daniel Kubitschek at the Univ. of Colorado (with George Born as thesis 
advisor) looked at th effects
of solar array warping and ran tests with GEODYN. This is documented in 
the paper.

Kubitschek, D., and G. Born, Modelling the anomolous acceleration and 
radiation pressure forces
for the TOPEX/Poseidon spacecraft, Phil. Trans. R. Soc., 359, pp. 
2191-2208, 2001.

See the URL: 
http://rsta.royalsocietypublishing.org/content/359/1788/2191.abstract

I reproduce the abstract below, but in a nutshell Dan found that 
modelling these effects
did not substantially improve the orbit performance. The caveat is we 
have since that time vastly improved
our modelling capabilities (GRACE-derived gravity models, modelling of 
time-variable gravity, better
station coordinates for the SLR/DORIS stations, better modelling of 
ocean tides etc.). I attach a summary
of the current standards in our recomputed orbits (std0905) along with a 
summary of the improvements
in the TOPEX POD fits, as documented in the paper of Lemoine et al. 
(2010, Adv. Space Research
DORIS SPecial Issue, In Review). Perhaps a revisit of the solar array 
warp issue on T/P is warranted.

Finally this solar array warp issue was of some concern to the POD team 
on T/P as in the references
to Kubitschek paper above, we have this TM from CSR, that maybe John 
Ries could make available
in pdf form on an ftp site, if it is not too much trouble.

Kar, S. and J.C. Ries (1993), The effect of solar array warping on TOPEX 
orbit determination,
Technical memorandum, CSR-TM-93-02, Center for Space Research, 
University of Texas.

Hopefully people will find this message a useful summary.

Best regards,

Frank Lemoine
===========

Abstract of Kubitschek and Born Phil. Trans. Paper.
Modelling the anomalous acceleration and radiation pressure
forces for the TOPEX/POSEIDON spacecraft
Daniel G. Kubitschek and George H. Born
Author Affiliations

Colorado Center for Astrodynamics Research,
Aerospace Engineering Sciences, University of Colorado
Campus Box 431, Boulder, CO 80309, USA
Abstract

A few months after launch of the TOPEX/POSEIDON (T/P) spacecraft, during 
the verification phase of the mission, the Precision Orbit Determination 
Team discovered residual along–track accelerations which were unexpected 
and of unknown origin. This paper describes the analysis of radiation 
forces acting on the T/P spacecraft for the purpose of understanding and 
providing an explanation for the anomalous accelerations. The radiation 
forces acting on the solar array, which experiences warping due to 
temperature differences between the front and back surfaces, are 
analysed and the resulting along–track accelerations are determined. 
This analysis led to the development of a new radiation force model 
which includes (1) warping of the solar array, (2) solar array 
deployment deflections as large as 2°, (3) necessary adjustments to 
certain surface property parameters, and (4) an adjustment to the 
coefficient of drag. As a result of the new model, estimates of the 
empirical constant along–track acceleration are significantly reduced in 
magnitude and are less dependent upon the location of the Sun relative 
to the orbit plane.