  A recent occultation measurement of the dwarf planet Haumea (Ortiz et al.
2017) revealed an elongated shape with the longest axis comparable to Pluto's
mean diameter. The chords also indicate a ring around Haumea's equatorial
plane, where its largest moon, Hi'iaka, is also located. The Haumea occultation
size estimate (equivalent diameter 1595 km) is larger than previous radiometric
solutions (in the range between 1150 and 1350 km), which lowers the object's
density to about 1.8 gcm-3, a value closer to the densities of other large
TNOs. We present unpublished and also reprocessed Herschel and Spitzer MIR and
FIR measurements. We compare 100 and 160um thermal lightcurve amplitudes -
originating from Haumea itself - with models of the total measured system
fluxes (ring, satellite, Haumea) from 24-350um. The combination with results
derived from the occultation measurements show that Haumea's crystalline water
ice surface must have a thermal inertia of ~5 SIu. We also have indications
that the satellites (at least Hi'iaka) must have high geometric albedos >=0.5,
otherwise the derived thermal amplitude would be inconsistent with the total
measured system fluxes at 24, 70, 100, 160, 250, and 350um. The high albedos
imply sizes of about 300 and 150 km for Hi'iaka and Namaka, respectively,
indicating unexpectedly high densities >1.0 gcm-3 for TNOs this small, and the
assumed collisional formation from Haumea's icy crust. We also estimated the
thermal emission of the ring for the time period 1980-2030, showing that the
contribution during the Spitzer and Herschel epochs was small, but not
negligible. Due to the progressive opening of the ring plane, the ring emission
will be increasing in the next decade when JWST is operational. In the MIRI
25.5um band it will also be possible to obtain a very high-quality thermal
lightcurve to test the derived Haumea properties.
