What secret military technology did this device conceal? Well, none. It was the "mission" it was flown on, also expounded upon by the Smithsonian some time earlier (June/July 2005 issue), "The Notorious Flight of Mathias Rust".
At the time, the general perception conveyed in the U.S. press, was this was an amusing stunt performed by a naive but somewhat unbalanced and delusional extremist.
(And, perhaps he was...Mathias Rust).
But to his credit, he had done some thinking (on things besides flight planning: 550 nm flight was at the far end of the Cessna's range): "To many Europeans, Mikhail Gorbachev’s ascendancy to the Soviet leadership in 1985 offered a glimmer of hope. Glasnost, his policy of transparency in government, and perestroika, economic reforms at home, were radical departures from the policies of his predecessors. So when the U.S.-Soviet summit in Reykjavik, Iceland, in October 1986 ended without an arms reduction deal, Rust felt despair. He was particularly angered by Reagan’s reflexive mistrust of the Soviet Union, which Rust felt had blinded the president to the historic opportunity Gorbachev presented."
Reykjavik Summit, Oct 11-12, 1986.
With today, November 9, being the 20th anniversary of the nominal observation of the "fall of the Berlin Wall", I think the humble Cessna 172 deserves it's due credit.
From U.S. News and World Report, June 15, 1987:
"Mathias Rust surely had no thoughtof doing Mikhail Gorbachev a favor. But last week, Gorbachev was trying to turn what could have been humiliation into opportunity by undercutting the old military establishment and launching what may be the long-awaited mopup of opponents--military and civilian --who impede his reforms. Rust's tiny plane, which he had flown unscathed through vaunted Soviet air defenses, was still parked near Red Square when Gorbachev began firing and promoting military brass. His dismissal of Defense Minister Sergei Sokolov, 75, appeared only the first step in a purge of recalcitrant officers."
Gorbachev and glasnost: viewpoints from the Soviet Press by Isaac J. Tarasulo, Dec 1989):
"For two years Gorachev did not attempt to interfere with military personnel decisions. While military leaders supported Gorbachev's call for revitalizing the Soviet economy, they believed themselves exempt from these changes. Exempt, that is, until May 1987. On May 28, 1987, nineteen-year-old Mathias Rust landed his Cessna 172 in Red Square..."
NYTimes, June 1, 1987:
A Test for Gorbachev...
"The scalding public indictment of the military signaled that even the most revered and powerful institutions would be subject to open criticism...Since taking office in March 1985, Mr. Gorbachev has pressed to hold down growth in military spending and has pursued a number of foreign policy initiatives, including an 18-month moratorium on underground nuclear testing, that have troubled the military." (How's that go again, that we forced the Soviet Union to economic collapse with an arms spending race?)
"Tear Down This Wall". (Ronnie reads his lines, on June 12, 1987. He was in Germany to bolster support for Pershing II nuclear missile deployments in Europe).
Two weeks after the Cessna 172 landed.
Reagan ends his second term, on Jan 21, 1989.
"In May of 1989, Soviet President Mikhail Gorbachev visited West German Chancellor Helmut Kohl. Gorbachev told Kohl the Soviets would not block democratic reforms in Warsaw Pact nations".
In June 1989, the Polish elections legitmize Solidarity.
On August 23, 1989, Hungary removed its physical border defences with Austria, and in September more than 13,000 East German tourists in Hungary escaped to Austria.
The East German head of state Erich Honecker, from 1971 until 1989, is forced by his own Poltiburo to resign on October 18, 1989. (The big significance: "In 1961, Honecker, as the Central Committee secretary for security matters, was in charge of the building of the Berlin Wall.")
"East German government announced on November 9, 1989, after several weeks of civil unrest, that all GDR citizens could visit West Germany and West Berlin."
"The fall of the Berlin Wall paved the way for German reunification, which was formally concluded on October 3, 1990."
What a wonderful moment in history, to be celebrated! It was amazing how fast Germany reunification happened- I remember estimates of the year 2020-2040. (Erich Honecker, The Party Leader in East Germany:"The Wall will be standing in 50 and even in 100 years, if the reasons for it are not yet removed." (Berlin, 19 January 1989).