ESA UNCLASSIFIED – For Official Use FMTM#101: ESATAN-TMS PTSINK - sink temperature data interpretation, Columbus J. Persson Noordwijk 20/11/2015

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 2 ESA UNCLASSIFIED – For Official Use Background – Columbus thermal modelling 1.Since the start of the programme, dating back to the 90’s, the ISS elements have been modelled generally assuming diffuse reflectivity both for solar and IR radiation 2.Columbus is covered with Micrometeoroid and Debris Protection Shield (MDPS) panels, which are made from aluminium with a Chromic Acid Anodization (CAA) surface treatment 3.While the surface treatment, CAA, is the same also for other elements, notably Node 2 and Node 3, it has not been done in the same way, resulting in differences in reflectivity (see following slide). The more shiny look of Columbus, next to Node 2, is a sign of more specular reflectivity 4.As long as payload or equipment was not planned to remain in close vicinity of the module, including the specular reflective component of the Columbus MDPS in the modelling was not regarded as needed

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 3 ESA UNCLASSIFIED – For Official Use Columbus imagery – exterior surface Columbus MDPS CAA Typical  = 0.28/0.31 Node MDPS Typical  = 0.33/0.44

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 4 ESA UNCLASSIFIED – For Official Use Columbus Ka-Band Terminal (Colka) 1.With the start in 2013 of the work on Columbus Ka-Band Terminal (Colka), which is meant to be attached to the MDPS, the issue of the thermal interaction with Columbus had to be addressed 2.For a first estimate for the most favourable locations for radiators, to support the optimisation of the equipment configuration, a thermal analysis was performed with the Columbus GMM/TMM from the launch campaign in 2007/2008

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 5 ESA UNCLASSIFIED – For Official Use Colka sink temperature analysis #1 (1) 1.In order to study the sink temperature in all directions, ±X/±Y/±Z, a dummy box, =1, =1, with all sides 0.25 m, was added on the anticipated Colka location

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 6 ESA UNCLASSIFIED – For Official Use Colka sink temperature analysis #1 (2) 1.The worst-case hot orbit parameters were based on a previous analysis in 2002, when for the first time adding an antenna to Columbus was studied ISS attitude:XVV, YPR [-15°/-15°/-15°] Beta angle:-75° (winter solstice) Solar flux: W/m 2 Planet IR:286.1 W/m 2 Albedo:0.4 Altitude:277.8 km

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 7 ESA UNCLASSIFIED – For Official Use 1.In order to extract the data on sink temperature, the PTSINK function in ESATAN-TMS was used 2.In the 2013 analysis, the Columbus MDPS was still considered with diffuse reflectivity 3.PTSINK generates three types of sink temperatures ( see Rationale and definitions for the implementation of sink temperatures in ESATAN, ESA memorandum TOS- MCV/2003/2921/ln/OP ) Black body sink temperature: Grey body sink temperature: Radiative sink temperature: where  i A i B ij equals GR ij Colka sink temperature analysis #1 (3)

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 8 ESA UNCLASSIFIED – For Official Use 1.The results for the dummy box, which are identical for black-body and grey-body sink temperatures, predictably show that the zenith- pointing surface has the best radiator orientation Colka sink temperature analysis #1 (4) Surface37 (nadir)38 (port)39 (forward)40 (starboard)41 (aft)42 (zenith) Sink temperature (black body) Orbit position

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 9 ESA UNCLASSIFIED – For Official Use 1.At the PDR for the Colka platform earlier in 2015, it was decided to study the potential effect of specular reflectivity on the Colka thermal control 2.To form an idea of the sensitivity, the 2013 analysis was revisited 3.The analysis was rerun changing the solar-band reflectivity of the Columbus MDPS such that a mixed reflectivity with a specular component of 0.2 was included, simultaneously reducing the diffusive part with the same amount 4.While there were only a few cases showing an effect on the box temperature, there was a major impact on the PTSINK results. There is no longer a correlation between surface temperature and black-body and grey-body sink temperatures 5.The Gebhart factors for sink temperature calculation apply only to diffusely reflecting surfaces. However, in the current problem, the specular component is only present in the solar band Colka sink temperature analysis #2 (1)

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 10 ESA UNCLASSIFIED – For Official Use Only for two surfaces, 38 and 42, clear changes were seen in the output temperature 2.Even when the external flux components in the solar band were forced to zero, the disconnect between surface temperature and sink temperatures, and between sink temperatures, remains Colka sink temperature analysis #2 (2)

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 11 ESA UNCLASSIFIED – For Official Use 1.Discussion with Philippe Poinas, previously involved in the PTSINK definition, has not led to a conclusive answer why the results appear 2.In order to have a more simple case to study, thermal modelling has been done with a two-node configuration, with a black surface perpendicular to a surface with thermo-optical properties emulating the Columbus MDPS (polar orbit, 90° inclination, 500 km altitude, 45° angle to sun) 3.The results have do not show the same trend as for the ISS Colka sink temperature analysis #2 (3)

FMTM#101 | J. Persson | Noordwijk | 20/11/2015 | TEC | Slide 12 ESA UNCLASSIFIED – For Official Use 1.For the simplified configuration, the view factor between surfaces #1 and #2 is 0.2. By direct calculation, one can that the solar absorbed flux for the black surface has to be 1152 W with only diffuse reflectivity and 1313 W with mixed reflectivity (1145 W/1307 W in previous table) 2.It leaves the question: What goes wrong for the ISS? 3.All suggestions are welcome… P.S. In the meantime, measurements on remaining samples of the Columbus MDPS have shown that the specular reflectivity forms more than half of the total reflectivity Conclusion