A method for detecting gravitational memory is proposed. It makes use of ingoing null geodesics instead of timelike geodesics in the original formulation by Christodoulou. It is argued that the method is applicable in the bulk of a spacetime. In addition, it is shown that BMS symmetry generators in Newman-Unti gauge have an interpretation in terms of the memory effect. This generalises the connection between BMS supertranslations and gravitational memory, discovered by Strominger and Zhiboedov

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... t null infinity, to the bulk. 1 Blanchet and Damour [5] independently obtained the same result. 2 See [6] for a geometric approach that goes beyond the weak-field analysis. See [7, 8] for statements about the memory effect in black hole spacetimes.