This is an obvious error. The US 7,439,877 patent citation is the correct one because it is in the same space and has the same inventor as the patent in question. The two identifiers are only off by a single digit and have the same publication date:
US7439877 May 18, 2007 Oct 21, 2008 Philip Onni Jarvinen Total impedance and complex dielectric property ice detection system
US7439887 * Feb 13, 2007 Oct 21, 2008 Seiko Epson Corporation Method and apparatus for GIF decompression using fixed-size codeword table
* Cited by examiner
For what its worth, using integers as a unique identifier is error-prone (due to OCR errors and human transpositions, as you mention).
Now, I think there are some other interesting issues with this patent grant. Nowhere in the document is there a reference to an application. The priority date and filing date are identical:
March 30, 2009, which means there was no provisional application. Nowhere in the document does the grant claim the benefit of the priority of other applications or grants.
The USPTO records and Google Patents records agree on the lack of a recorded patent application.
However, looking at the Espacenet record, we see the following:
Application number: US20090383894 20090330
Priority number(s): US20090383894 20090330
However, the application US20090383894 does not exist in Google Patents or the USPTO database.
Searching in the USPTO Public Pair system for
12/383894, we can find some interesting information about the application. It has a lengthy list of actions, including abandonment, withdrawal of abandonment, "Request for Applicant Statement Regarding Potential NASA Interest", and a request for special consideration due to advanced age of the inventor. The application itself (US 2009/0383894) is also contained in the Image File Wrapper.
Also in the Image File Wrapper is the Examiner's search strategy and published results:
04-01-2010 SRNT Examiner's search strategy and results
which is followed on the same day with a document containing US 7,439,887 as Prior Art:
04-01-2010 892 List of references cited by examiner PRIOR ART
The terms and class codes that the Examiner searched should not have turned up US 7,439,887. It is in class 341, and search was restricted to class 340. Human error.