ULTRASAT is the first major Time Domain Explorer of the Dyanmic UV Sky. It is a proposed "Partnership Mission of Opportunity" (PMO) between Israel (Weizmann) and US (Caltech, JPL). The Israeli effort is funded and Caltech/JPL are seeking NASA support via SALMON-2 opportunity.

On December 15, 2016 we submitted a proposal for Phase A. We will come to know of the outcome in May 2017. If selected we will enter Phase A. During this period we will refine the goals and complete a detailed engineering design (and most importantly undertake an extensive analysis for the cost). This phase will last for 15 months. NASA will then review our end-of-phase A study report. If selected once more we will enter Phase BCDE in early 2019 with launch in 2023. The prime phase lasts for 2.5 years. The on-board consumables and orbit allow us to operate for at least 5 years and perhaps longer.

Band of Operation 220--280 nm
Field of View 210 sq degrees
FWHM of PSF 25 arcsec (1 pixel=8.5 arcsec)
Basic Frame time 3x300 s
5-sigma sensitivity 21.5 AB mag
Orbit Geo-synchronous + 300 km
TOO capable Yes
Launch 2021
Prime phase 30 months
Pointing Strategy 6 months NEP (Northern Winter), 6 months SEP (Southern Winter)
TOO capability (50% of sky within hour) All sky survey

The satellite will be a "ride share" with a geo-comm satellite (Launch Provider: Space Science Loral). However, we will be launched into a geo-synch + 300 km orbit. The satellite will drift 3 degrees to an observer on earth.

Data will be continuously streamed (lossless) and analysis undertaken in real time to the Mission Operations Center (MOC; Israel Aerospace Industry) and transient analysis undertaken at the Science Operations Center (SOC; Level 1, Weizmann Institute of Science). Alerts can be issued typically within ten minutes. Level 2 processing will be undertaken within the same day at the Science & Data Analysis Center (SDAC; IPAC, Caltch) and curated. Images can be coadded in real time for higher SNR (e.g. stack 3 frames to get 21.3 AB mag, stack 18 frames to get an hourly average and so on).

The current pointing strategy is to stare at a low extinction region close to the North Ecliptic Pole (NEP) during the Northern winter and then switch to staring at the South Ecliptic Pole region during the Southern Winter. Thus at the end of the mission (nominal, 30 months) we will have four data sets, each lasting 6 months and with a cadence of 3x300 s.

The nominal two pillars are: early studies of supernovae (shock breakout & shock cooling) and AGN (reverberation mapping, accretion disk tomography). Other science areas that are listed are Tidal Disruption Events, Stellar Activity, Relativistic Explosions (Orphan, Dirty Fireball), and Exoplanets. Speculative returns (known unknowns): Binary SMBH, EM+GW and IceCube events.
A paper by Sagiv et al. (2014AJ....147...79S) has many details of ULTRASAT version 1 goals and architecture. For ULTRASAT version 3 (this version), as noted above, we are now proposing a different orbit (geo versus sun-synch), one large FOV telescope (not several).