Black nickel coatings exhibiting high infrared emittance were developed on copper and stainless steel substrates by pulse electrodeposition using a modified Fishlock bath. The uniform jet black coating is intended to provide passive thermal control of spacecraft components. Space worthiness of the coating was evaluated by conducting a series of space environmental tests such as humidity, thermal stability, thermal cycling and thermo-vacuum performance tests. The thermo-optical properties namely solar absorptance (alpha (s)) and infrared emittance (epsilon(IR)) of the coatings were measured before and after each environmental test. No significant change in thermo-optical properties was observed after environmental tests showing their high stability for spacecraft thermal control applications. The coatings were characterized by cross-sectional SEM and EDX, XRD, XPS, Nanoindentation and Nano Vision analysis. X-ray diffraction pattern reveals the amorphous nature of the coating with possible presence of ZnS. XPS analysis confirms the chemical and electronic state of the elements. Average modulus and hardness of the coating was recorded using Nanoindentation method and a high resolution 3D image of the surface was generated using Nano Vision scan.