Blockstream's Bitcoin satellite service aims to increase the robustness and accessibility of the Bitcoin network. Here's a summary of the service, along with its advantages and disadvantages:

Summary:

Blockstream Satellite broadcasts the Bitcoin blockchain from space, allowing anyone with a satellite dish to receive Bitcoin block data without the need for an internet connection. The main idea is to make Bitcoin accessible in regions without reliable internet infrastructure and to provide redundancy for the Bitcoin network.

Advantages:

Accessibility: It enables people in areas with limited or no internet access to participate in the Bitcoin network.

Redundancy: Even if parts of the internet are shut down or censored, the Bitcoin network can continue to operate, ensuring its resilience.

Privacy: Using the satellite can provide an additional layer of privacy, as users don't need to connect to the traditional internet to receive blockchain data.

Fixed Cost: Once the satellite dish and equipment are set up, receiving data is generally without ongoing costs, as opposed to internet data plans which might charge by the amount of data used.

Disadvantages:

Initial Setup Cost: Users need specific hardware, including a satellite dish and a receiver, which might be expensive or difficult to obtain in some regions.

Technical Complexity: Setting up and pointing a satellite dish, and configuring the necessary software, can be complex for users without technical expertise.

One-way Communication: The satellite service is primarily for broadcasting data. If users want to make a transaction, they'll need another way to broadcast it (unless combined with another service like mesh networks).

Coverage Limitations: While the satellite network has extensive coverage, it doesn't cover 100% of the Earth's surface.

Potential for Centralization: Depending on its usage and reliance, it could introduce a central point of potential failure or control. Blockstream is the entity behind the satellite, and over-reliance could theoretically introduce risks.

In conclusion, Blockstream's satellite service is an innovative approach to increasing Bitcoin's robustness and accessibility. It addresses some key challenges in Bitcoin adoption but also introduces new challenges and considerations.