also: にあって
in; at; during; under (circumstances)
Formal conjunction indicating a situation, time, or condition in which something occurs. Often used in written or formal speech. にあっては is more common than にあって.
In an emergency, calm judgment is required.
現代社会にあっては、情報の管理が重要だ。
In modern society, information management is important.
In such an emergency, calm judgment is required.
In modern society, the accuracy of information is important.
に当たって marks the moment of undertaking an action ('when doing X'), while にあっては marks the surrounding situation or circumstance ('in such a situation'), so they aren't interchangeable despite both sounding formal.
Derived from the particle に + the て-form of ある (ありて → あって) + topic particle は. Literally 'being in/at', it grammaticalized into a formal conjunction.