Friday 10 August 2012, by cneiner
| Specification | Minimal requirement | Goal | Comment |
|---|---|---|---|
| Wavelength range | 117-320+390-870 nm | 90-1000 nm | This UV range contains many diagnostic transitions for hot stars and galaxies. The optical domain covers most of the important lines for both hot and cool stars, from CaII H&K to the Ca triplet, and including the Balmer and Paschen jumps. Polarimetry in the UV would allow direct measurement of polarization in the wind. |
| UV resolution | 25000 | 100000 and 2000 | 100000 is needed to resolve lineprofiles in stellar spectra. 2000 is needed for faint targets |
| UV S/N | 100 | 200 | enough for most diagnostics |
| Optical resolution | 35000 | 80000 | needed to resolve line profiles and Stokes signatures in stellar spectra |
| Optical S/N | 100 | 300 | needed to detect weak magnetic fields |
| Polarization | V in lines | QUV in lines and continuum | circular polarization (V) is needed to measure magnetic fields, full polarization (VQU) is needed to study disks and full magnetospheres. Continuum polarization is very useful to study dusty environments. |
| Instrumental polarization | 3% | 1% | On the ground, we manage < 1% |
| Accuracy in radial velocity | 1 km/s | 0.3 km/s | Required for e.g. Doppler Imaging |
| Target magnitude | V=3-10 | V=2-15 | |
| Targeted stars | 50 | 100 | |
| Time per targeted star | 4 weeks | 6 weeks (4+1+1) | Some hot stars rotate very fast (of the order of 1 day), other targets have rotation periods of several weeks. We considered that on average the rotation period is 2 weeks. |
| Survey stars | 4000 | 8000 | |
| Time per survey star | 20 min | 30 min | |
| Mission duration | 4 years | 12 years | The mission duration derives from this mean rotation period and the number of targets. |