Isru chag

Isru Chag (Hebrew: אסרו חג‎, lit. "Bind [the] Festival") refers to the day after each of the Three Pilgrimage Festivals in Judaism: Pesach, Shavuot and Sukkot.

The phrase originates from the verse in Psalms 118:27, which states, “Bind the festival offering with cords to the corners of the altar.” This verse, according to the Sages of the Talmud, should homiletically be understood to mean “Whosoever makes an addition to the Festival by eating and drinking is regarded by Scripture as though he had built an altar and offered thereon a sacrifice.”

In a responsum to a community that had inquired as to the rationale behind the observance of Isru Chag, Rabbi Yosef Hayyim (1832 - 1909), known as the Ben Ish Chai, cited the famous Kabbalist Rabbi Isaac Luria (1534 - 1572), known as the ARI, to the effect that we [Jews] connect the day after the holiday to the holiday itself due to the remaining “light” of the holiday – in other words, so that the sanctity of the holiday will be extended.

Rabbinic authorities cite observances

In situ resource utilization

In space exploration, in-situ resource utilization (ISRU) is defined as "the collection, processing, storing and use of materials encountered in the course of human or robotic space exploration that replace materials that would otherwise be brought from Earth." ISRU is the practice of leveraging resources found or manufactured on other astronomical objects (the Moon, Mars, asteroids, etc.) to fulfill or enhance the requirements and capabilities of a space mission.

ISRU can provide materials for life support, propellants, construction materials, and energy to a spacecraft payloads or space exploration crews. It is now very common for spacecraft and robotic planetary surface mission to harness the solar radiation found in situ. The use of ISRU for material production has not yet been implemented in a space mission, though several field tests in the late 2000s demonstrated various lunar ISRU techniques in a relevant environment.

ISRU has long been considered as a possible avenue for reducing the mass and cost of space exploration architectures, in that it may be a way to drastically reduce the amount of payload that must be launched from Earth in order to explore a given planetary body. According to NASA, "in-situ resource utilization will enable the affordable establishment of extraterrestrial exploration and operations by minimizing the materials carried from Earth."