  The Gamow Explorer will use Gamma Ray Bursts (GRBs) to: 1) probe the high
redshift universe (z > 6) when the first stars were born, galaxies formed and
Hydrogen was reionized; and 2) enable multi-messenger astrophysics by rapidly
identifying Electro-Magnetic (IR/Optical/X-ray) counterparts to Gravitational
Wave (GW) events. GRBs have been detected out to z ~ 9 and their afterglows are
a bright beacon lasting a few days that can be used to observe the spectral
fingerprints of the host galaxy and intergalactic medium to map the period of
reionization and early metal enrichment. Gamow Explorer is optimized to quickly
identify high-z events to trigger follow-up observations with JWST and large
ground-based telescopes. A wide field of view Lobster Eye X-ray Telescope
(LEXT) will search for GRBs and locate them with arc-minute precision. When a
GRB is detected, the rapidly slewing spacecraft will point the 5 photometric
channel Photo-z Infra-Red Telescope (PIRT) to identify high redshift (z > 6)
long GRBs within 100s and send an alert within 1000s of the GRB trigger. An L2
orbit provides > 95% observing efficiency with pointing optimized for follow up
by the James Webb Space Telescope (JWST) and ground observatories. The
predicted Gamow Explorer high-z rate is >10 times that of the Neil Gehrels
Swift Observatory. The instrument and mission capabilities also enable rapid
identification of short GRBs and their afterglows associated with GW events.
The Gamow Explorer will be proposed to the 2021 NASA MIDEX call and if
approved, launched in 2028.
